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You should also take a look at SurveyCTO (www.surveycto.com), which is built on top of Open Data Kit. It has all the functionality that you outlined - in particular the ability to capture GPS coordinates, distances between coordinates, and plot areas - and is designed for offline data collection even in very resource constrained settings. Basically, no ...


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You cannot get PDOP from HDOP. PDOP brings in a vertical dimension (VDOP) which is rarely made available separately. Your options are: to calculate it yourself from the geometry at the time (i.e. if you know which satellites were in solution at any given time; and you know the resulting position; you could derive it). make some assumptions which are ...


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yes there are many GNSS RTK receivers example STONEX GNSS or North GNSS that they send NMEA to the BlueTooth Also you could read the manuals from Javad and other GNSS ventors to intergrate in your application their GNSS futures. you can use the SSP example to connect to them Example Application is on Google Play the MyRTK


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As I understand your question, at 19 cm wave length, you need to measure the phase to get down to cm (or even mm) accurate positioning. However, the measure phase is actually always of py 2*pi*i where "i" is an integer. In other words, to measure the actual phase of the wave, you first need to figure which wave needs to measured.


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Mapbox has a plugin for mapbox.js to help snap and clean up GPS traces. https://github.com/mapbox/mapbox-match.js.


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The Trimble R1 offers Galileo support: http://www.trimble.com/R1-GISUser Capable of supporting multiple satellite constellations, including GPS, GLONASS, Galileo and BeiDou


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You can use PostGIS for this. To perform vertical datum transformations, you'll have to add your own SRID to the spatial_ref_sys table with the appropriate WKT and proj4 parameters. For example, if you query the spatial_ref_sys table for NAD83(CSRS) UTM12 (EPSG:2956), select proj4text from spatial_ref_sys where srid=2956; you get: +proj=utm +zone=12 ...


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This http://forum.xda-developers.com/showthread.php?t=1479209 thread has your answer. Shortly, it uses the Mac address of the AP to determine approximately where you are.


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The best solution I have found so far is : QLandkarte GT It does all the actions I have listed and much more. The only trick is to get map overlay, but it is easier with the latest version. It is worth to mention that it's multiplateform software.


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This looks like bad multipath effects I have seen - but those are generally seen when capturing features near (within 2 foot of) high reinforced concrete walls. Different environment but the effects look quite suspiciously similar. External antennas are supposed to have better multipath rejection. And you might do better using an offset (preferably ...


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Pathfinder Office (or other post-processing software) knows the position of the base station, Almanac and Emphemeris (downloaded from Internet) allow PFO to work out the position of each of the satellites every second, and the base data provides pseudo-range (code) measurements) and Carrier measurements. From the base location and satellite positions, PFO ...


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I assume the positions which do not post-process are in similar GPS conditions to positions which do post-process (i.e. you are not randomly walking under trees every hour and standing in the open the rest of the time.) In my experience (I use Trimble TerraSync and PathFinder Office post-processing at least once a week) the most likely cause of problems ...


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Try Orux maps. It has the capability to download tiles for offline use, load KML overlays and load raster for background imagery. Not sure though it has all the functionality you need in terms of KML attributes but it is worth a try.


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The German Wikipedia explains also a closed form solution for the four sphere equations: https://de.wikipedia.org/wiki/GPS-Technik#L.C3.B6sungsverfahren_f.C3.BCr_4_Gleichungen_mit_4_Unbekannten However, I don't know whether it is actually used by current GPS Receivers.


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There are two versions that I was taught on a GPS course (admittedly a lot of years ago): take partial differential equations of the distance equations (with an unknown time error) a closed form solution by Steve Bancroft (which I knew as the "King Radio" method, but since King got absorbed by Bendix, then by some other avionics manufacturer, that ...



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