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Questions tagged [gps]

This tag refers generically to *any* space-based satellite navigation system that provides location and time information.

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30
votes
9answers
16k views

Creating polyline-based “heatmap” from GPS tracks?

This winter I am planning to track my downhill skiing/snowboarding using a GPS. Most of my riding will occur at the same resort. I would like to be able to create a sort of "heatmap" that shows the ...
2
votes
3answers
6k views

Local Coordinate to Geocentric

The ultimate question, I need a transformation matrix to take a point in local space representing a roughly 500m x 500m place in New Mexico centered at -108.619987456 long 36.234600064 lat. The final ...
17
votes
9answers
13k views

Seeking Mobile Data collection software recommendations?

What COTS software is available to do mobile data collection, with GPS positioning. Map display not required. I'm looking across the board (platform wise). I'm already aware of... RhinoSpect ArcPad ...
43
votes
5answers
146k views

What is the maximum Theoretical accuracy of GPS?

I was talking with a potential client, and they requested that we plot some points with GPS, with a maximum (or should that be minimum?) accuracy of 2 m. This is an area with no WAAS, and I was under ...
21
votes
3answers
15k views

What causes the GPS offset/shift in China?

I've spent close to two full days trying to understand the nature of the infamous GPS shift in China. After sifting through the noise, two recurring symptoms are that: GPS coordinates (WGS-84) plot ...
8
votes
10answers
4k views

Device for Logging GPS and Accelerometer Data? [closed]

I am looking for a device that can track my location (lat,long) and speed all day long. Perhaps, I need GPS and accelerometer data bundled together. What I want to do is to log my daily activities. I ...
35
votes
9answers
18k views

Is there a good GPS track analysis library?

I keep writing custom code to work with GPS tracks: GPX files and NMEA logs from my phone, dedicated GPS logger, etc. I feel like I'm reinventing the wheel and am wondering if there's some standard ...
52
votes
9answers
116k views

Why does GPS positioning require four satellites?

I have a question on the GPS positioning algorithm. In all books I've read for 3D positioning we need four satellites, and I don't understand why. We need to calculate three variables: x, y, z. We ...
13
votes
5answers
6k views

How to build a geographic database of GPS logs?

On our aerial wildlife surveys we typically generate dozens of GPX files, and usually convert most of them into shapefiles for display in a GIS application. GPX files are a terrific way of keeping all ...
12
votes
5answers
12k views

Convert XY points to a line?

Someone mistakenly saved a GPS track as waypoints and then sent them along to me in a .csv file. They want a line back (shapefile). What's the simplest method to convert this to a line? Available ...
4
votes
4answers
14k views

Can *.ssf files from Trimble GPS be imported as features to display in ArcMap?

I have not come across *.ssf files before but I believe they are a Trimble GPS binary format. Someone has asked me if these files which he thinks have line/poly features can be imported for display ...
0
votes
1answer
15k views

Converting Degree Minutes to decimal degrees using Excel formula? [duplicate]

I have location points collected from a garmin device stored in an excel sheet in Degree Minutes format --- W00208.172,N1046.977. I am looking for an Excel formula to convert either to Decimal ...
18
votes
1answer
1k views

Statistically calculating real road from set of GPS tracks?

I participate in a long-distance cycling club, and we started to collect GPS data routinely from our riders. My interest is to calculate "the real trajectory" for future events based on accumulated ...
7
votes
5answers
5k views

Matching GPS tracks

I'm looking for a proper way to process multiple GPS tracks (so time ordered list of lat/lon points) and match/classify that segments, that are covered by multiple tracks: So it's not about recording,...
31
votes
2answers
56k views

Differences between triangulation and trilateration?

Looking around I noticed that many people interchange the terms (triangulation and trilateration) for the same sense. What is the correct sense of Triangulation and what are the differences from ...
18
votes
7answers
4k views

Sources of realtime spatial data [closed]

I'm trying to set up a demo that serves up live spatial data, but am having trouble finding any suitable example data sources. Ideally I'm looking for something that updates every few seconds; either ...
12
votes
10answers
6k views

Need a Benchmark GPS Trajectory data-set?

I'm looking for a benchmark GPS data set, available for research purposes for free. I've found GeoLife GPS Trajectories dataset from Microsoft Research but I find it a little incomplete. What I need ...
13
votes
3answers
10k views

Post processing GPS data with open source software

I am using Magellan Professional Mapper CX working on ArcPad 7.1 platform. It has sub-meter accuracy after post processing. Without post processing the data collected in the field is off by 10 to 15 ...
11
votes
2answers
13k views

What algorithm should I use to remove outliers in trace data?

I have GPX traces and want to remove outlying observations. There are some route points that are impossible because it would require acceleration that the vehicle can not achieve. Are there good ...
9
votes
1answer
654 views

Approximating GPS coordinates for a point from n expected locations

I'm trying to find the coordinates of my point of attention (point X,marked blue). I used the GPS device of my car to collect the coordinates according to where I parked my vehicle each time I visited ...
2
votes
3answers
12k views

Distance between GPS coordinates

Given a database of GPS points, a center GPS location, and a radius R (in meters), how can I find all points in the database that are within a distance of R of the center point? Will the distance iso-...
40
votes
12answers
34k views

Tablet or smart phone GPS vs “real” GPS

I've been reading a lot today about android and iphone devices being used for spatial data collection in the field and it sure seems to be that single purpose devices such as the extremely popular ...
15
votes
5answers
12k views

How to get an elevation profile for a gps track?

I'd like to get a reasonably accurate elevation profile for a track recorded with a GPS (which often has very unreliable altitude data and occasionally none at all, depending on the model.) Does ...
11
votes
2answers
1k views

Create “mean” line from multiple lines using QGIS

I have multiple lines features (also have them in multipoints...) representing similar path (mountain trails, in this case) with various GPS precision, resulting in many lines close to each other, but ...
23
votes
2answers
7k views

How much sense does it make to average (lat,lon) samples in order to increase 2D accuracy of a GPS location?

Several GPS applications, like this one, or this one, acquire multiple (lat,lon) samples of a given location, assuming that the GPS unit is not moving, and then take an average of the samples in order ...
8
votes
2answers
4k views

Using OpenLayers (with OpenStreetMaps) and PostGis for rendering data acquired from GPS tracking device?

I'm researching and planing to acquire data from GPS device and store them in postGIS database, then use geodjango to process/work them out and finally chart them on a map with OpenLayers. Will these ...
7
votes
7answers
16k views

Cleaning/editing GPX (tracks) files recorded from GPS device in QGIS?

During a long trip, I have recorded tracks of my journey with the GPS of my smartphone. I have ended up with about 30 GPX datafiles. Now that I am back, I am trying to draw a map of this trip. I ...
6
votes
2answers
2k views

QGIS live GPS tracking /recommended hardware (GPS USB stick) [closed]

Is there a list or any other recommendation of certain GPS hardware (esp. GPS USB sticks) working with QGIS? I have been off this topic for far over a decade, and i remember that in former days not ...
3
votes
1answer
18k views

How do I calculate a xyz-position of one GPS position relative to another?

I have two GPS positions (lon, lat, alt) and want to get the position of one relative to the other one. (in meters, as x, y, z) How do I do that? Edit: The locations have a distance of up to three ...
9
votes
1answer
15k views

Batch converting Garmin GDB to GPX?

I need to convert a lot of garmin GDB files to GPX in order to convert it to another vector format. Is there any tools available can do a batch convert from garmin GDB files to GPX? Using MapSource ...
9
votes
3answers
3k views

Using PROJ.4 library to transform from local coordinate system coordinates to global coordinate system using ground control points?

I have a point cloud whose coordinates are with respect to a local coordinate system. I also have ground control points with GPS values. Can I convert these local coordinates to a global coordinate ...
7
votes
1answer
1k views

Connect / Disconnect GPS device via PyQGIS

In QGIS I would like to establish a connection to my GPS device programmatically (not via button in the GPS control panel) I found out how to get available ports with QgsGPSDetector i.e. ...
7
votes
1answer
2k views

If the GPS navigation message takes 12 1/2 minutes to cycle, how can receivers update your position every second?

According to Wikipedia's article on GPS, Each GPS satellite continuously broadcasts a navigation message... Each complete message takes 750 seconds (12 1/2 minutes) to complete. My understanding ...
7
votes
2answers
1k views

Managing error with GPS routes (theoretical framework?)

I'm looking for the appropriate theoretical framework or speciality to help me deal with understanding how to deal with the errors that the GPS system has - especially when dealing with routes. ...
2
votes
2answers
21k views

How to export and import gps points from Garmin 62S and QGIS

I'm pretty new to using QGIS and I'm curious about how to import and export GPS points created in QGIS. I have QGIS 2.0.1 Dufour on Windows XP and a Garmin 62s. Any suggested walk throughs would be ...
0
votes
1answer
4k views

Using the Live tracking with internal GPS? [closed]

We have some Panasonic ToughPads (FZ-G1) with a GPS a module built in. I know where it is and can locate in it in COM 3 and it connects, registers a signal, shows satellite locations, but refuses to ...
6
votes
2answers
8k views

What is a GPS epoch?

What is a GPS epoch? I encounter this often in technical discussions and it does not have a clear meaning to me. Lately it was used in this post and it seems to mean the receiver update rate (the ...
4
votes
2answers
2k views

Alternative to Terrasync for Trimble Windows Mobile unit

I have a number of Trimble Nomad 900 series devices and am currently using TerraSync. TerraSync does the job, but are there any other alternatives out there that would be even simpler to use? ...
3
votes
1answer
530 views

Automatically panning the map in ArcGIS when using the Time slider

I have a point dataset with time-stamps at 1 minute intervals showing a driving route. I have enabled the Time properties of the layer and I am able to use the Time slider to see the points move ...
2
votes
1answer
876 views

Accessing GPS from QGIS 2.14.1/Python 2.7 /Windows10

I would like to access the device described at QGIS live GPS tracking /recommended hardware (GPS USB stick) via QGIS/Python. A gps module does't seem to be part of the standard installation of python ...
1
vote
2answers
2k views

Automating production of GPS-compatible map tiles from georeferenced raster maps [closed]

I have a set of TIFF maps that I want to load onto Garmin GPS 62s units. The maximum size for each tile on the GPS is 3Mb and less than 1 million pixels. I manually produced one tile, following this ...
26
votes
6answers
16k views

How correct is the “Accuracy” value given by GPS devices?

I have a Garmin Forerunner 305 and a Google Nexus One Android phone. From the GPS on both these devices I can get a "Accuracy" value that is usually between 6-20 meters. How much can I trust this ...
30
votes
7answers
5k views

Why don't they use cell towers like GPS satellites?

If my understanding is correct, a GPS satellite produces a pretty simple signal which is basically composed of its location and its time. Given 4 of these signals, then one can uniquely solve for the ...
14
votes
5answers
17k views

Clustering trajectories (GPS data of (x,y) points) and mining the data

I've got 2 questions on analyzing a GPS dataset. 1) Extracting trajectories I have a huge database of recorded GPS coordinates of the form (latitude, longitude, date-time). According to date-time ...
13
votes
3answers
11k views

Advanced android app for mapping and GPS logging?

I am looking for an android app able to log GPS data like coordinates, altitude, current speed and would be nice if also the GPS accuracy/number of satellites. Many GPS apps are able to display these ...
10
votes
3answers
9k views

Calculate maximum speed from GPS data

I have raw GPS locations for a track, and need to get maximum speed. Simple methods (calculate speed between 2 points, take max) will give meaningless large numbers due to GPS inaccuracy, the point is ...
14
votes
1answer
2k views

How to find ring of coverage of GPS Satellite on WGS-84 ellipsoid?

Given the following: Time, t The set of IS-200 Ephemeris data, E, of a GPS Satellite corresponding to time t The ECEF position of the GPS satellite, P=(x,y,z), derived from the time and ephemeris, (t,...
17
votes
3answers
582 views

Lightsquared GPS controversy: Where is the analysis?

GPS World reports that Lightsquared's network of 40,000 transmitters will interfere with GPS signals. Initial technical analyses have shown that the distant, low-powered GPS signals would ...
9
votes
6answers
6k views

Detecting and fixing outliers in a GPS trajectory

I need to find an algorithm or method that can detect outlier latitude longitude points in a trajectory during post-processing, which can then be fixed (brought back into the trajectory's path based ...
9
votes
4answers
37k views

Making work tablet integrate GNSS (GPS) on Windows 8 with QGIS?

I have tablet - Dell latitude 10, running Windows 8, with integrated Broadcom GNSS Receiver BCM47511 (GPS,Glonass...). Because it is integrated GPS and Windows 8, there is the "new" way of providing ...