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What's the most accurate elevation tool on the net (freebie)
What elevation tool do you use and how does it compare in accuracy?
I'm trying to do some antenna siting calculations ... and ... for that ... I need elevation information. However ... given any set of coordinates ... e.g., Mt Hamilton, California at coordinates 37.337408,-121.644073 ... I find the following elevation tools all give DIFFERENT elevations (some are off by more than a hundred feet!) 1. Google Map API yields 1217.061889648438 meters (3992.985 feet) http://maps.googleapis.com/maps/api/elevation/json? locations=37.337408,-121.644073&sensor=false 2. Geoplaner yields 1217.1 meters (3993 feet) http://www.geoplaner.com 2. Daftlogic yields 1230.988 meters (4038.676 feet) http://www.daftlogic.com/sandbox-goo...d-altitude.htm 4. Earthtools yields 1210 meters (3969.8 feet) http://www.earthtools.org 5. Heywhatsthat (SRTM db) yields 1213 meters (3980 feet) http://www.heywhatsthat.com/profiler-0904.html Q: Which elevation tool do you use ... & what's the accuracy? |
What's the most accurate elevation tool on the net (freebie)
Unless you are dealing with a surveyed peak, I would assume all the elevation data is derived from USGS NEDs (national elevation dataset). For the most part, they are only 1/3 arc second. I'm speculating that some of these programs are reporting data from the NEDs as if they are section of flat areas on the 1/3 arc second grid, while others are interpreting the elevation using a weighting scheme. http://seamless.usgs.gov/ Have you considered running SPLAT! ? It uses 1/3 arc second data. It can predict line of sight. Generally I find I do better than the SPLAT! prediction, so if SPLAT! says no, the answer is maybe, but if SPLAT! says yes, you have line of sight. The program has hooks for predicting signal strength, models knife edge diffraction, etc. http://www.qsl.net/kd2bd/splat.html Similar software is http://www.cplus.org/rmw/english1.html For pure line of sight, there is GRASS. However GRASS has a very steep learning curve. http://grass.osgeo.org/ What takes maybe 5 minutes on SPAT can take 2 days on GRASS. I don't know if the results are that much better. For the bay area, I suspect SPLAT! is fine. I think it's shortcomings are in areas where there is really rugged terrain that probably isn't modeled well. |
What's the most accurate elevation tool on the net (freebie)
On Sat, 3 Mar 2012 04:02:49 +0000 (UTC), alpha male
wrote: What elevation tool do you use and how does it compare in accuracy? I'm trying to do some antenna siting calculations ... and ... for that ... I need elevation information. However ... given any set of coordinates ... e.g., Mt Hamilton, California at coordinates 37.337408,-121.644073 ... I find the following elevation tools all give DIFFERENT elevations (some are off by more than a hundred feet!) 1. Google Map API yields 1217.061889648438 meters (3992.985 feet) http://maps.googleapis.com/maps/api/elevation/json? locations=37.337408,-121.644073&sensor=false 2. Geoplaner yields 1217.1 meters (3993 feet) http://www.geoplaner.com 2. Daftlogic yields 1230.988 meters (4038.676 feet) http://www.daftlogic.com/sandbox-goo...d-altitude.htm 4. Earthtools yields 1210 meters (3969.8 feet) http://www.earthtools.org 5. Heywhatsthat (SRTM db) yields 1213 meters (3980 feet) http://www.heywhatsthat.com/profiler-0904.html Q: Which elevation tool do you use ... & what's the accuracy? Youre asking wrong questions. First define a surface with height ZERO as a reference. There are about 100 different definitions alone for that. Distance from Earth center, median sea level at Novosibirsk, or a San Francisco? Water isn't level, it follows gravitation. And so on. w. |
What's the most accurate elevation tool on the net (freebie)
On Sat, 03 Mar 2012 04:02:49 +0000, alpha male wrote:
What elevation tool do you use and how does it compare in accuracy? I'm trying to do some antenna siting calculations ... and ... for that ... I need elevation information. However ... given any set of coordinates ... e.g., Mt Hamilton, California at coordinates 37.337408,-121.644073 ... I find the following elevation tools all give DIFFERENT elevations (some are off by more than a hundred feet!) 1. Google Map API yields 1217.061889648438 meters (3992.985 feet) http://maps.googleapis.com/maps/api/elevation/json? locations=37.337408,-121.644073&sensor=false 2. Geoplaner yields 1217.1 meters (3993 feet) http://www.geoplaner.com 2. Daftlogic yields 1230.988 meters (4038.676 feet) http://www.daftlogic.com/sandbox-goo...d-altitude.htm 4. Earthtools yields 1210 meters (3969.8 feet) http://www.earthtools.org 5. Heywhatsthat (SRTM db) yields 1213 meters (3980 feet) http://www.heywhatsthat.com/profiler-0904.html Q: Which elevation tool do you use ... & what's the accuracy? I'd use the info from another licensee's application, (on the same tower). With the FCC you also must specify which survey you are using. All towers over 200'(AIR) have their own entry in a tower database. |
What's the most accurate elevation tool on the net (freebie)
On Sat, 03 Mar 2012 00:10:32 -0800, miso wrote:
Have you considered running SPLAT! I just installed the Splat (Surface Path Length And Terrain) RF analysis application (version 1.3.0-1) from the default Ubuntu Software Center. - http://joysofprogramming.com/install-splat-ubuntu/ - $ sudo apt-get install splat (dpkg -s splat) It's apparently a command-line tool which needs me to download the database so it may take a while to figure out. Googling for a "splat!" tutorial, I find it's also a photoshop hack so it's actually hard to figure out how to use it on the fly. Q: Do you have a working example or two for how to use it from the command line? Quote:
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What's the most accurate elevation tool on the net (freebie)
In rec.radio.amateur.antenna alpha male wrote:
What elevation tool do you use and how does it compare in accuracy? I'm trying to do some antenna siting calculations ... and ... for that ... I need elevation information. However ... given any set of coordinates ... e.g., Mt Hamilton, California at coordinates 37.337408,-121.644073 ... I find the following elevation tools all give DIFFERENT elevations (some are off by more than a hundred feet!) 1. Google Map API yields 1217.061889648438 meters (3992.985 feet) http://maps.googleapis.com/maps/api/elevation/json? locations=37.337408,-121.644073&sensor=false 2. Geoplaner yields 1217.1 meters (3993 feet) http://www.geoplaner.com 2. Daftlogic yields 1230.988 meters (4038.676 feet) http://www.daftlogic.com/sandbox-goo...d-altitude.htm 4. Earthtools yields 1210 meters (3969.8 feet) http://www.earthtools.org 5. Heywhatsthat (SRTM db) yields 1213 meters (3980 feet) http://www.heywhatsthat.com/profiler-0904.html Q: Which elevation tool do you use ... & what's the accuracy? GPS 3 meter error |
What's the most accurate elevation tool on the net (freebie)
On Sat, 03 Mar 2012 15:59:39 +0000, alpha male wrote:
splat | less http://www.kgiwireless.com/Documents...icSiteList.asp http://www.americantower.com/sitelocator/default.aspx |
What's the most accurate elevation tool on the net (freebie)
On 3/3/2012 7:59 AM, alpha male wrote:
On Sat, 03 Mar 2012 00:10:32 -0800, miso wrote: Have you considered running SPLAT! I just installed the Splat (Surface Path Length And Terrain) RF analysis application (version 1.3.0-1) from the default Ubuntu Software Center. - http://joysofprogramming.com/install-splat-ubuntu/ - $ sudo apt-get install splat (dpkg -s splat) It's apparently a command-line tool which needs me to download the database so it may take a while to figure out. Googling for a "splat!" tutorial, I find it's also a photoshop hack so it's actually hard to figure out how to use it on the fly. Q: Do you have a working example or two for how to use it from the command line? Quote:
SPLAT! isn't a photoshop hack, but you can use gimp (or I suppose photoshop) to hack with the png files it creates. I take the png files and chop them up so they are acceptable to google earth, then make an overlay out of them. Splat can do it, but unless things have changed, it makes a kml file that can be too large for GE to accept. GE wants tiled imagery. I haven't run it in maybe 18 months, so I can't really say much without setting it up again. I saw a GPS mentioned. I never found GPS elevation to be too accurate. I have a barometer in my GPS. I never used it, so I can't vouch for it's accuracy. But you can enter in the pressure from the airport, or calibrate it to a known reference (known altitude for a position). One idea would be to check the USGS monuments and find the closest reference. http://www.ngs.noaa.gov/cgi-bin/datasheet.prl Note that sometimes these markers are on private property. Other times they are in the middle of the street! it pays to look at the reference on google earth before trying to use it. My Garmin gps60cs was good to 4ft, basically one lsb. You could get a nearby reference, call the barometer, then quickly move to your spot before the pressure changes. Or you might get lucky and find there is a marker there already. Topo maps have lines of constant altitude, usually on 20ft contours. You could interpolate from the map. If you really need accurate data, just pay for a survey. I would guess something that simple is under a grand. I've paid for land surveys and they are a few grand, but the altitude at one point is pretty simple. Potentially the civil engineering firm might have topo data on file that is not available to the general public. For instance, I paid for a satellite topo to be done on some property. The civil engineering firm has it on file and I'm sure it gets peeked at by other people. |
What's the most accurate elevation tool on the net (freebie)
On Sat, 03 Mar 2012 09:13:45 +0100, Helmut Wabnig [email protected] ---
-.dotat wrote: Youre asking wrong questions. First define a surface with height ZERO as a reference. There are about 100 different definitions alone for that. Distance from Earth center, median sea level at Novosibirsk, or a San Francisco? Water isn't level, it follows gravitation. And so on. w. If in the US, I would assume that the LAT/LONG uses either WGS84, NAD27, or NAD83 datums. That reduces the number of available options. Unfortunately, the USGS is still hanging onto NAD27, while most mapping programs and displays are on WGS84. http://www.maptools.com/UsingUTM/mapdatum.html In the People's Republic of Santa Cruz, the error is about 20 meters east-west, and about 1 meter north-south. I forgot which way. The problem becomes really bad when trying to locate a mountain top. 20-200 meters of horizontal error can easily move a position from the peak, to somewhere on the slope, resulting in large altitude errors. SRTM and SRTM2 are another oddity. They were created from the space shuttle, using a radar altimeter. Depending on the whether it's looking at buildings or trees, there's no really good way to determine of the indicated altitude is the top of a 100ft redwood tree, the top of a 10 meter high building, or at ground level. So, my list of rhetorical questions a 1. What is the OP trying to accomplish? If for an FCC license HAAT calculation, almost any reasonable guess will suffice. http://transition.fcc.gov/mb/audio/bickel/haat_calculator.html If for doing Radio-Mobile coverage contours, you'll need to use the built in mapping tool to find the peak or exact location on the mountain top. The choice of application depends on what one is attempting to accomplish. 2. What level of accuracy is really required? The original position of 37.337408N -121.644073W is specified to 1 millionth of a degree, or about 0.09 meters. http://www.csgnetwork.com/degreelenllavcalc.html It would be interesting to know where this highly accurate number came from. Better GPS receivers, without DGPS, can do 3 meters accuracy. 3. What datum are you using? I suggest WGS84. If the lookup tool offers a choice of datums, pick one and stay with it. 4. Are you interested in ground level, building rooftop level, or tree top level? -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com # http://www.LearnByDestroying.com AE6KS |
What's the most accurate elevation tool on the net (freebie)
Jeff Liebermann wrote:
On Sat, 3 Mar 2012 18:47:56 -0000, wrote: GPS 3 meter error Yep. However, standing under the tower, in order to take advantage of this level of accuracy is often impractical. Climbing barbed wire topped chain link fences is not my idea of fun. I ran into the problem when I was throwing together a map of the local cell sites: http://802.11junk.com/cellular/ (from about 2002). I had a suitable GPS, but I couldn't get anywhere near some of the towers in order to get an accurate position. I had to record a GPS location nearby, measure or estimate the distance and direction to the tower, and then do the math. My objective was to determine my full Maidenhead before there were web applications to find it. I just took my portable, WAAS enabled, aviation GPS to the back yard and let it average for a couple of minutes. Since then I discovered why I kept getting different results pre-GPS (long boring story about map accuracies); turns out the dividing line runs down the sidewalk across the street. |
What's the most accurate elevation tool on the net (freebie)
On Sun, 4 Mar 2012 20:10:17 -0000, wrote:
My objective was to determine my full Maidenhead before there were web applications to find it. Some GPS receivers will deliver the Maidenhead grid square directly. http://www.n7cfo.com/vhf/gps/~gps.htm I just took my portable, WAAS enabled, aviation GPS to the back yard and let it average for a couple of minutes. Since then I discovered why I kept getting different results pre-GPS (long boring story about map accuracies); turns out the dividing line runs down the sidewalk across the street. Chuckle. We're close to that problem at the local club station (K6BJ): http://802.11junk.com/jeffl/pics/drivel/slides/grid-cm8x.html I had to post this map because operators were constantly calculating the wrong grid square. Nearby, is the local intersection of the lat-long lines. http://confluence.org http://confluence.org/confluence.php?lat=37&lon=-122 Notice the wide variations in photos by people thinking they've found the correct location. The problem is that the real intersection is located on a poison oak infested steep hillside. We posted a DGPS located marker, but people keep stealing it. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
What's the most accurate elevation tool on the net (freebie)
Jeff Liebermann wrote:
On Sun, 4 Mar 2012 20:10:17 -0000, wrote: My objective was to determine my full Maidenhead before there were web applications to find it. Some GPS receivers will deliver the Maidenhead grid square directly. http://www.n7cfo.com/vhf/gps/~gps.htm I just took my portable, WAAS enabled, aviation GPS to the back yard and let it average for a couple of minutes. Since then I discovered why I kept getting different results pre-GPS (long boring story about map accuracies); turns out the dividing line runs down the sidewalk across the street. Chuckle. We're close to that problem at the local club station (K6BJ): http://802.11junk.com/jeffl/pics/drivel/slides/grid-cm8x.html I had to post this map because operators were constantly calculating the wrong grid square. Nearby, is the local intersection of the lat-long lines. http://confluence.org http://confluence.org/confluence.php?lat=37&lon=-122 Notice the wide variations in photos by people thinking they've found the correct location. The problem is that the real intersection is located on a poison oak infested steep hillside. We posted a DGPS located marker, but people keep stealing it. As it turns out, my house is in the very SW corner of DM14fco7, with the front in DM14fco7ae and the back in DM14fco7be. mandatory antenna content If you go to http://no.nonsense.ee/qthmap/ and enter DM14fco7be the white dot in the middle of the back yard is the box covering an SGC autotuner for the 33 foot vertical. |
What's the most accurate elevation tool on the net (freebie)
On Sat, 03 Mar 2012 19:43:47 -0800, Jeff Liebermann wrote:
What is the OP trying to accomplish? The neighbors and are discussing setting up a neighborhood mesh network and we need to ascertain, beforehand, where to place masts and which direction to point them in our mountainous neighborhood (Skyline & Summit area). If for an FCC license HAAT calculation, almost any reasonable guess will suffice. For us, probably any reasonable answer would suffice - but why not pick the most accurate for starters is what we're thinking. What level of accuracy is really required? The original position of 37.337408N -121.644073W is specified to 1 millionth of a degree, or about 0.09 meters. A few feet would probably work just fine for the neighborhood. We each have acres of land, but the terrain is so rough that only a few spots for antennas would be useful. That's why we want to choose them ahead of time. It would be interesting to know where this highly accurate number came from. We didn't want to put our actual location on the net, so, we picked an arbitrary set of numbers from one of the elevation calculators just as an example. But we're in the roughly 37,-122 range. What datum are you using? I suggest WGS84. WGS84. We have some numbers in NAD83 from the various WISP providers but they drive us crazy since we have to imperfectly convert them to WGS84 to keep our numbers consistent. Are you interested in ground level, building rooftop level, or tree top level? All three because we want to site a dozen or more antennas which need to have clear line of sight over rooftops and trees by at least the first Fresnel zone. |
What's the most accurate elevation tool on the net (freebie)
On Sat, 03 Mar 2012 19:43:47 -0800, Jeff Liebermann wrote:
http://www.maptools.com/UsingUTM/mapdatum.html Interesting quotes from that helpful reference (with my comments in parenthesis). "In the Continental United States the difference between WGS 84 and NAD 27 can be as much as 200 meters." (I wonder how they handle the constant creep which occurs out here near the San Andreas fault line). "Every map that shows a geographic coordinate system such as UTM or Latitude and Longitude with any precision will also list the datum used on the map." (I'd change "will" to 'should' based on my experience the past two weeks on the web) "The Global Positioning System uses an earth centered datum called the World Geodetic System 1984 or WGS 84." (That's what I prefer.) "For all practical purposes there is no difference between WGS 84 and NAD 83." (Good to know.) "On a USGS topographic map ... The datum will always be NAD 27... A dashed cross in the SW and NE corners of the map gives a visual indication of the difference between the two datums." (This is good to know.) "If you are engaged in a mission that requires more [than several hundred meters] precision, then your datums should match." (Since we're siting antennas on private hilly land, we probably want two or three meters accuracy in position and a half-meter to a meter in elevation accuracy so our datums must match.) |
What's the most accurate elevation tool on the net (freebie)
On Mon, 05 Mar 2012 15:30:57 +0000, alpha male wrote:
On Sat, 03 Mar 2012 19:43:47 -0800, Jeff Liebermann wrote: (I wonder how they handle the constant creep which occurs out here near the San Andreas fault line). What I mean by that is that it's a right-slip fault, and it moves by centimeters to inches each year (sometimes in feet to yards, both in elevation and in position) ... but ... how do they know if the west side moved north or if the east side moved south? I wonder what they use for their frame of reference since it depends on which side of the fault you're on if you want to say the west moved north or that the east moved south. |
What's the most accurate elevation tool on the net (freebie)
On Mon, 5 Mar 2012 15:09:40 +0000 (UTC), alpha male
wrote: On Sat, 03 Mar 2012 19:43:47 -0800, Jeff Liebermann wrote: What is the OP trying to accomplish? The neighbors and are discussing setting up a neighborhood mesh network and we need to ascertain, beforehand, where to place masts and which direction to point them in our mountainous neighborhood (Skyline & Summit area). Ok. Go thee unto: http://www.cplus.org/rmw/english1.html Follow the destructions at: http://www.cplus.org/rmw/download/download.php?S=1 For maps, download the SRTM3 maps for your area from: http://rmw.recordist.com Do not bother with DEM, SRTM1, or other maps. Do NOT unzip the maps. My directory shows about 600MBytes of SRTM3 data for everything for the SF Bay and Monterey Bay areas. You can set Radio-Mobile to automatically download a map if needed, but it's easier to just download the maps ahead of time. Follow a simple example such as: http://www.cplus.org/rmw/afirst.html to get started. There are also numerous tutorials on the web. Note that the program uses the concept of "networks" which will be key to modeling a mesh. Locate your nodes, use realistic values, and build a model. This part is a PITA and requires considerable time and effort. Draw the (optical) coverage areas for each node, and the line of sight: http://joelgranados.wordpress.com/2011/11/05/wireless-link-calculations-radio-mobile/ You're going to have a big problem in the Santa Cruz Mountains call trees. These are cellulose and water obstructions that may or may not appear at the correct altitude on the elevation profiles. 2.4GHz will NOT penetrate foliage, especially when wet. You'll need to manually adjust your path profiles for the tree line. If the trees are inside the Fresnel zone, you'll have losses. If you have problems, ask here, or preferably the Yahoo Radio-Mobile group at: http://groups.yahoo.com/group/Radio_Mobile_Deluxe/ I have a really bad attitude about mesh networks. Bug me if you want to hear the full rant. For a sample, see the dismal performance of an early mesh network (MIT Roofnet - Meraki). http://pdos.csail.mit.edu/roofnet/doku.php?id=interesting "Surprisingly, the performance over a two hop route is less than 1/2 that of one hop routes, implying routes tend to interfere with themselves." Also: http://sha.ddih.org/2011/11/26/why-wireless-mesh-networks-wont-save-us-from-censorship/ covers the main problems. Do you really want a phone call at 2AM from a neighbor asking if the network is down? -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
What's the most accurate elevation tool on the net (freebie)
On Sat, 03 Mar 2012 19:43:47 -0800, Jeff Liebermann wrote:
http://transition.fcc.gov/mb/audio/bickel/haat_calculator.html This is an interesting antenna HAAT (Height Above Average Terrain) program ... but I'm not quite sure what use it is because it gives a 360 degree average height ... but most 2.4Ghz antennas I'm dealing with are directional. You enter the latitude, longitude, & height of the antenna, and then it tells you, for example, for 360 degrees, the average antenna height above ground for 2 to 10 miles along each radial, the result of which can go negative. The output is a text file. It's interesting, but, without graphics, I'm not sure how to use the results properly when just going point to point. |
What's the most accurate elevation tool on the net (freebie)
On Mon, 5 Mar 2012 19:46:16 +0000 (UTC), alpha male
wrote: On Sat, 03 Mar 2012 19:43:47 -0800, Jeff Liebermann wrote: http://transition.fcc.gov/mb/audio/bickel/haat_calculator.html This is an interesting antenna HAAT (Height Above Average Terrain) program ... but I'm not quite sure what use it is because it gives a 360 degree average height ... but most 2.4Ghz antennas I'm dealing with are directional. You enter the latitude, longitude, & height of the antenna, and then it tells you, for example, for 360 degrees, the average antenna height above ground for 2 to 10 miles along each radial, the result of which can go negative. I wrote that before you disclosed what you were trying to accomplish. Had your intent to obtain accurate altitude readings been for the purpose of applying for an FCC station license, you would have needed the HAAT calculations to estimate coverage area. For building you mesh network, you don't need HAAT calculations. http://en.wikipedia.org/wiki/HAAT The first paragraph should explain what HAAT means. The output is a text file. It's interesting, but, without graphics, I'm not sure how to use the results properly when just going point to point. Hint: You can always take a table of number and create a graph or graphic. Going the other direction is not so easy. Most propagation and antenna design software generates an output table (text file), from which a graphic is later generated. -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com # http://www.LearnByDestroying.com AE6KS |
What's the most accurate elevation tool on the net (freebie)
On 3/5/2012 8:26 AM, Jeff Liebermann wrote:
On Mon, 5 Mar 2012 15:09:40 +0000 (UTC), alpha male wrote: On Sat, 03 Mar 2012 19:43:47 -0800, Jeff Liebermann wrote: What is the OP trying to accomplish? The neighbors and are discussing setting up a neighborhood mesh network and we need to ascertain, beforehand, where to place masts and which direction to point them in our mountainous neighborhood (Skyline& Summit area). Ok. Go thee unto: http://www.cplus.org/rmw/english1.html Follow the destructions at: http://www.cplus.org/rmw/download/download.php?S=1 For maps, download the SRTM3 maps for your area from: http://rmw.recordist.com Do not bother with DEM, SRTM1, or other maps. Do NOT unzip the maps. My directory shows about 600MBytes of SRTM3 data for everything for the SF Bay and Monterey Bay areas. You can set Radio-Mobile to automatically download a map if needed, but it's easier to just download the maps ahead of time. Follow a simple example such as: http://www.cplus.org/rmw/afirst.html to get started. There are also numerous tutorials on the web. Note that the program uses the concept of "networks" which will be key to modeling a mesh. Locate your nodes, use realistic values, and build a model. This part is a PITA and requires considerable time and effort. Draw the (optical) coverage areas for each node, and the line of sight: http://joelgranados.wordpress.com/2011/11/05/wireless-link-calculations-radio-mobile/ You're going to have a big problem in the Santa Cruz Mountains call trees. These are cellulose and water obstructions that may or may not appear at the correct altitude on the elevation profiles. 2.4GHz will NOT penetrate foliage, especially when wet. You'll need to manually adjust your path profiles for the tree line. If the trees are inside the Fresnel zone, you'll have losses. If you have problems, ask here, or preferably the Yahoo Radio-Mobile group at: http://groups.yahoo.com/group/Radio_Mobile_Deluxe/ I have a really bad attitude about mesh networks. Bug me if you want to hear the full rant. For a sample, see the dismal performance of an early mesh network (MIT Roofnet - Meraki). http://pdos.csail.mit.edu/roofnet/doku.php?id=interesting "Surprisingly, the performance over a two hop route is less than 1/2 that of one hop routes, implying routes tend to interfere with themselves." Also: http://sha.ddih.org/2011/11/26/why-wireless-mesh-networks-wont-save-us-from-censorship/ covers the main problems. Do you really want a phone call at 2AM from a neighbor asking if the network is down? I've used Radio Mobile and SPLAT!. I never got a warm and fuzzy with Radio Mobile. Of course, it is a bit more complicated to use SPLAT!. One obvious advantage to SPLAT! is it can analyze very large areas. Not all that useful in the case of this wifi setup, but very useful in sigint. |
What's the most accurate elevation tool on the net (freebie)
On Tue, 06 Mar 2012 01:24:06 -0800, miso wrote:
On 3/5/2012 8:26 AM, Jeff Liebermann wrote: Ok. Go thee unto: http://www.cplus.org/rmw/english1.html Follow the destructions at: http://www.cplus.org/rmw/download/download.php?S=1 For maps, download the SRTM3 maps for your area from: http://rmw.recordist.com Oops. I meant the SRTM1 maps. http://dds.cr.usgs.gov/srtm/version2_1/SRTM1/ I've used Radio Mobile and SPLAT!. I never got a warm and fuzzy with Radio Mobile. Of course, it is a bit more complicated to use SPLAT!. I've used both. Radio-Mobile has a very steep learning curve. Important functions are buried deep into obscure menus, useless trivia is scattered all over the menus, there's no logical sequence of operation, and many of the terms require expertise in cartography. Debugging errors is tricky as important items, such as the performance characteristics of the radios, are scattered over a half dozen menu pages. I find myself constantly referring to my cheat sheet in order to get anything done. However, I haven't found anything else that even comes close to what it does. One obvious advantage to SPLAT! is it can analyze very large areas. Not all that useful in the case of this wifi setup, but very useful in sigint. http://www.qsl.net/kd2bd/splat.html Splat is somewhat easier to use, but as you note, is designed to display repeater coverage. It's less useful for close in coverage, or showing coverage details, as in mountainous or urban jungle terrain. Both programs put considerable effort into implementing complex terrain models. For 2.4 and 5.7Ghz, optical line of sight is close enough. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
What's the most accurate elevation tool on the net (freebie)
On Mon, 05 Mar 2012 08:26:29 -0800, Jeff Liebermann wrote:
If you have problems, ask here, or preferably the Yahoo Radio-Mobile group at: http://groups.yahoo.com/group/Radio_Mobile_Deluxe/ The first problem I'm having is locating a Linux (Ubuntu) Radio Mobile download ... |
What's the most accurate elevation tool on the net (freebie)
On Tue, 6 Mar 2012 19:13:12 +0000 (UTC), alpha male
wrote: On Mon, 05 Mar 2012 08:26:29 -0800, Jeff Liebermann wrote: If you have problems, ask here, or preferably the Yahoo Radio-Mobile group at: http://groups.yahoo.com/group/Radio_Mobile_Deluxe/ The first problem I'm having is locating a Linux (Ubuntu) Radio Mobile download ... Is that suppose to be some kind of thanks for doing your research? In the future, if you need assistance, get it from someone else. RM mostly runs under Wine: http://radiomobile.pe1mew.nl/?How_to:Wine The problems listed are not fatal as you can download the SRTM maps manually, and can simply export the result as a Google Earth overlay to obtain street map detail. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
What's the most accurate elevation tool on the net (freebie)
Oops. I meant the SRTM1 maps. http://dds.cr.usgs.gov/srtm/version2_1/SRTM1/ I've used Radio Mobile and SPLAT!. I never got a warm and fuzzy with Radio Mobile. Of course, it is a bit more complicated to use SPLAT!. I've used both. Radio-Mobile has a very steep learning curve. Important functions are buried deep into obscure menus, useless trivia is scattered all over the menus, there's no logical sequence of operation, and many of the terms require expertise in cartography. Debugging errors is tricky as important items, such as the performance characteristics of the radios, are scattered over a half dozen menu pages. I find myself constantly referring to my cheat sheet in order to get anything done. However, I haven't found anything else that even comes close to what it does. One obvious advantage to SPLAT! is it can analyze very large areas. Not all that useful in the case of this wifi setup, but very useful in sigint. http://www.qsl.net/kd2bd/splat.html Splat is somewhat easier to use, but as you note, is designed to display repeater coverage. It's less useful for close in coverage, or showing coverage details, as in mountainous or urban jungle terrain. Both programs put considerable effort into implementing complex terrain models. For 2.4 and 5.7Ghz, optical line of sight is close enough. My recollection of Radio Mobile is you need to crank down the minimum angle that it sweeps to get any accuracy. Like I said, I prefer SPLAT! for the accuracy. Even so, it is only as good as the NED. However, if SPLAT! says you can see it, then you can see it. I thought Radio Mobile was simple to run, at least for one transmitter at a time. Far easier than SPLAT, which requires compilation parameters to set the array size. Radio Mobile, at least when I read it, was stuck at 3600x3600. If you exceed that array, and note it uses a 1/3 arc second grid, the program interpolates. The grid is 10 meters on a size for 1/3 arc second. That means you can't "see" more than 36km. Plenty for wifi, not so good for repeaters or even photography. I generally do two runs with SPLAT. First I check the altitude when the radio is to be located. If it doesn't match the topo map, I add the difference in altitude to the transmitter height. Then run it again. I have a 90 mile path to analyze, so I guess I'll see what these programs can do lately. But if Radio Mobile is stuck at 3600 pixels, that is a show stopper. |
What's the most accurate elevation tool on the net (freebie)
RM mostly runs under Wine: http://radiomobile.pe1mew.nl/?How_to:Wine The problems listed are not fatal as you can download the SRTM maps manually, and can simply export the result as a Google Earth overlay to obtain street map detail. This guy got it going. ;-) http://forum.winehq.org/viewtopic.ph...ab4164 902614 If Alpha Male has linux, why even screw with Radio Mobile? Just run SPLAT!. For a small array, the KML SPLAT generates should be fine for Google Earth. My issue was the array was too big to feed GE directly. GE has an "aperture" size that doesn't appear to be consistent between PCs. GE expects the images to be tiled with no tile larger than the aperture. On my PC, that is 3600x3600. That is probably why you could load the Radio Mobile output to GE. Incidentally, there are programs designed to take a PNG and tile it, but I never got them to work. But it has been a while since I tried them. |
What's the most accurate elevation tool on the net (freebie)
On Tue, 06 Mar 2012 19:14:32 -0800, miso wrote:
My recollection of Radio Mobile is you need to crank down the minimum angle that it sweeps to get any accuracy. True. 1 degree resolution at perhaps 20km is: tan(1deg) * 20km = 350 meters resolution. Not great resolution, but good enough for wide area coverage. For wi-fi, the range is much less, so the "squares" shown on the map will be correspondingly smaller. Samples of wide coverage area RM calcs. http://802.11junk.com/jeffl/coverage/k6bj/ We recently moved our tower and antenna, when the building that previously supported them was demolished. So, I recalculated the coverage. I believe I used 1 degree resolution. than SPLAT, which requires compilation parameters to set the array size. Radio Mobile, at least when I read it, was stuck at 3600x3600. If you exceed that array, and note it uses a 1/3 arc second grid, the program interpolates. I'm too lazy to check the numbers right now. Maybe tomorrow. Meanwhile, this article claims that Splat is limited to 3600x3600 while Radio-Mobile is limited to 2000x2000. No clue at this time who's correct. I have a 90 mile path to analyze, so I guess I'll see what these programs can do lately. But if Radio Mobile is stuck at 3600 pixels, that is a show stopper. A 90 mile PATH (line) is quite different from a 90 mile radius coverage (area) radius. -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com # http://www.LearnByDestroying.com AE6KS |
What's the most accurate elevation tool on the net (freebie)
On Tue, 06 Mar 2012 19:52:36 -0800, Jeff Liebermann
wrote: On Tue, 06 Mar 2012 19:14:32 -0800, miso wrote: than SPLAT, which requires compilation parameters to set the array size. Radio Mobile, at least when I read it, was stuck at 3600x3600. If you exceed that array, and note it uses a 1/3 arc second grid, the program interpolates. I'm too lazy to check the numbers right now. Maybe tomorrow. Meanwhile, this article claims that Splat is limited to 3600x3600 while Radio-Mobile is limited to 2000x2000. No clue at this time who's correct. Looks like the balloon trackers have the same problem with Radio Mobile Deluxe. http://showcase.netins.net/web/wallio/RMD.html "The 2000x2000 software elevation matrix limits paths to 2000km for 1000m data (30-arc second), 200km for 100m data (3-arc second) and 130km for 30m data (1-arc second)." Now, go away so I can get some work done... -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com # http://www.LearnByDestroying.com AE6KS |
What's the most accurate elevation tool on the net (freebie)
It is a simple click to change the step size even down to 0.01 of a degree in the polar plot, or just run a Cartesian plot where you can specify down to one pixel resolution. Jeff Yes. I'm just mentioning cranking down the angle to save someone a few meaningless runs. It didn't occur to me to do the math as you suggested, but it makes perfect sense. I was running the beta version of splat-hd. I could do 6 degree x 6 degrees at 1/3 arc second. Each degree is 3600x3600, so I could do 21600x21600. If you want to do "mountain-topping", you need that kind of span. Looking at the overlays I generated, I had to hack the output into 12 to 20 blocks, 3600x3600 at a time, to make it google earth compatible. Hopefully the new version does this automatically. I believe this was the program I was trying to get to work to do the cookie cutting. Looking at the bug report, it still looks like it has issues. http://www.maptiler.org/ I got really good with GIMP to do the cookie cutting. Still a PITA. |
What's the most accurate elevation tool on the net (freebie)
On Monday, March 5, 2012 7:33:45 AM UTC-8, alpha male wrote:
On Mon, 05 Mar 2012 15:30:57 +0000, alpha male wrote: On Sat, 03 Mar 2012 19:43:47 -0800, Jeff Liebermann wrote: (I wonder how they handle the constant creep which occurs out here near the San Andreas fault line). What I mean by that is that it's a right-slip fault, and it moves by centimeters to inches each year (sometimes in feet to yards, both in elevation and in position) ... but ... how do they know if the west side moved north or if the east side moved south? I wonder what they use for their frame of reference since it depends on which side of the fault you're on if you want to say the west moved north or that the east moved south. WGS84 is a geographic coordinate system: it's referenced to the Prime Meridian and the Equator, not to any ground landmarks locally. the digital elevation data is "accurate as of the date of collection". If a fault moves or someone engages in a big earthmoving operation, then the data set won't reflect reality. As to the practical problem of determining plate movement? Easy if you have GPS, because GPS is referenced to WGS84, and WGS84 is referenced to a specific geoid, anchored at the equator and the prime meridian. In turn, one can use celestial landmarks to calibrate it. |
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