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

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How to calculate 'off track' error from GPS data?

I'd like to analyse navigational accuracy, comparing planned transects with the actual track flown from GPS data. For example, the planned transects below (green) don't match perfectly with the ...
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4answers
141 views

Accuracies of various GNSS systems

I was looking for a comparitive statement of the accuracies achived by various GNSS systems such as QNSS, COMPASS, GLONASS, GPS..etc. however i find only discriptions of only GPS everywhere
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236 views

Can I access Trimble logged positions in ArcMap10?

We recently walked a fence perimeter with a Trimble Ranger, auto-logging positions at 5 second intervals in a generic point file. The exported file acknowledges over 800 points, but only displays the ...
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2answers
75 views

Are speeds in GPS data obtained by detection or calculation?

I have been doing a study into taxi behavior with its GPS data. I could calculate taxi's mileage by either longitudes and latitudes or times and speeds in the data. Since there are several errors in ...
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1answer
2k views

What is required for post-processing differential correction? (And can Garmin units provide it?)

2 very closely related questions about differential correction with a Garmin unit: 1). Some data was collected using a Garmin GPSMAP 76Cx unit and the data collectors are interested in whether ...
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GPS Datalogger with USB Interface and GPX Output

I'm looking for a reliable, robust and reasonably priced GPS datalogger, to measure time, distance on tracks. The logger should be reasonably priced but ready for outdoor activities. Mud, dirt, a ...
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1answer
5k views

How can I convert Horizontal dilution of position to a radius of 68% confidence?

I am working at mobile app that uses external GPS module. What I need is to calculate accuracy for the fix from GPGGA command to be able to compare it with my mobile platform's GPS accuracy. Mobile ...
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1answer
457 views

Why are points collected with a Trimble FM 750 off by more than a mile when displayed in QGIS?

I have a grower that has a FM 750 and is trying to make points in a field. When finished he takes the file out of the display and goes to his computer and he can bring up the points in the right ...
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1answer
486 views

PLT track in PostGIS

What are the best practices for importing and aggregating tracks (in my case in 'plt' format) in a PostGIS table, grouped by user. Are there any tools/db models/tutorials available?
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1answer
55 views

How to improve GPS recording?

The image shows as example a small loop by car, recorded by two Garmin Dakota 10 devices. It seems both devices have had difficulties caused by the surrounding buildings, the "blue one" seemingly had ...
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Does iOS know the phone's location solely from cell tower, i.e. without GPS data?

Question Does the iOS operating system know the phone's location even if one could turn off the iPhone's built-in GPS module or if it was broken? Elaboration What I understand I understand that ...
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1answer
460 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 ...
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How to merge multiple file geodatabases into one file geodatabase?

I have created a file geodatabase that has several feature data sets, feature classes, and domains. I have created a map with the file geodatabase added to it, converted the map to ARCPAD AXF format ...
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1answer
522 views

How to connect particular sets of points with (poly)lines?

I think my problem is quite easy to be solved by the most postgis-users, but i am a bloody beginner: i have a timestamped point-table representing GPS-tracked places of different cars. To distinguish ...
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2answers
1k views

Garmin etrex 10 and QGIS

I want to know if anyone has been able to download data from a etrex 10/20/30 directly from Qgis. The usb protocol decsribe in a recent post does not do the trick. GpsBabel documentation states that ...
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1answer
449 views

Differentially correct GPX file

Is there any way to differentially correct a GPX file using free or open-source tools? Does a GPX file contain the necessary information for differential correction (I can put the timestamp in it ...
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1answer
134 views

How does a GPS unit ensure it has the same time reference as a GPS satellite?

I've been reading about GPS to find how it works, but one thing still bothers me. To calculate distance from GPS unit/receiver to GPS satellite, it uses the difference between radio signal sending ...
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229 views

Mapping Trails with GPS - Hardware Suggestions

I have been hired to map about 100km of XC ski trails. I am super proficient in GIS but have not done any detailed GPS work since college when I worked with some sort of Trimble explorers. This is a ...
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1answer
384 views

Sub-meter Bluetooth GPS units and ESRI Collector App

We have been using Trimble XT/XH for years now, but we are at a time when we need to upgrade and do not want to drop another $8000 for another Trimble that only causes us headaches and not very user ...
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0answers
317 views

GPS data based track/trip calculation algorithm available?

Currently I'm receiving position data of moving assets every 90 or 120 seconds (depending on the asset). What I'd like to achieve now is to detect standstill and movement phases (tracks/trips) on the ...
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3answers
4k views

Measuring polyline using either QGIS or ArcGIS Desktop?

I've collected a bunch of GPS polylines (WGS84). What is the easiest way to measure the length of these lines in KM using QGIS or ArcGIS Desktop?
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301 views

Differentiating a building from a road on a map?

This question was originally asked here by Steven and I felt the question was better asked here. Steven would also like to know the sources Google buys it maps from. I remember seeing a post about it ...
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443 views

How do I find software for my GPS?

I recently unearthed a GPS unit I purchased a few years. It's a Garmin GPSmap 60 (picture) and has a usb port on it. Is there a way that I can link it to my mac? I do have windows installed also, and ...
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3answers
2k views

Mobile, Offline viewer for geographic data

Currently, field crews consumer geographic data via laptop (no internet, no gps). ArcReader. I would like to get them shapefiles (or some derivative of a shapefile) on a mobile platform (smartphone) ...
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4answers
5k views

Connecting GPS to ArcGIS via USB

Is there a way to connect a GPS to ArcGIS via USB? At the moment the GPS extension only appears to support comm port connections. It would be good to know if a USB connection can be made, then perhaps ...
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2answers
166 views

Road segments reconstruction from GPS trajectories

We have a 10,000 base of vehicle mounted moving devices which report their GPS position on a time based schedule. All that data is currently being stored in our database for several business related ...
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304 views

gpspipe returns correct timestamp, but wrong date (21 dec 1995)

I'm having this strange issue where my gps pipe is returning the correct location and time but the wrong date (including year). For reference, at the time of writing it is 06 aug 2015, 09:27 UTC). ...
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160 views

Calculating new satellite position given pseudorange measurements

I'm looking for a reference/text for an explicit formula to calculate a satellite position given pseudorange measurements from later epoch times. I've seen a lot of matlab code on the internet but I ...
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1answer
195 views

Extract one GPS fix per day from data?

I am in the fortunate position of having 2 years worth of animal movement data. With such a large amount of data I would like to extract only one fix per day to make it easier to work with. Data = 14 ...
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1answer
240 views

Calculating speed along point feature class (.gpx) in ArcMap?

I have imported a .gpx file into ArcMap as a point feature class. Each feature has a Point z as well as a DateTime. I want to create a graph that shows speed as a function of distance. How do I do ...
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3answers
3k views

GPS post processing - Differential Correction

I have a large set of collected GPS points that I'm pulling into Arcgis from SQL and creating an xy event layer to then map them. The fields for the points are as follows: recorded, lat, long, ...
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3answers
180 views

Is there a service to check whether a gps path belongs to a public road?

I have a bunch of GPS tracks. I want to exclude the ones which go via public roads. I'm interested in off-road segments only. Is there any public api to check if a given set of coordinates belongs to ...
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621 views

Wildlife surveys using tablet and GPS, import/export to/from ArcMap

I've found some info about this on a previous post (Advanced android app for mapping and GPS logging), but it didn't provide enough info, I'm hoping some other tech experts can help! I have a tablet ...
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1answer
4k views

Distance calculation : Integrating incremental gps data

I am trying to build a GPS based odometer based on android. Currently , I am calculating incremental distance changes very frequently ( < 5 meter movement). The distance calculation in android is ...
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631 views

API to suggest nearby streets

For an app I'm developing, I want to use the phone's GPS to locate it. I then want it to list streets that are nearby. The customer might be in his back garden for example, and this may be closer to ...
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1answer
2k views

How to read multiple .gpx files in R [closed]

Suppose I have a number of .gpx files (these contain GPX waypoint data from a Garmin eTrex). I want to load them into R with different names and manipulate them. I can read one file thus: ...
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1answer
543 views

how to create a network from gps tracks?

I'm trying to build a network from several GPS-trakcs, to digitalize hiking routes on my land. I have several GPX-files from routes I've tracked with the gps. I managed to display them in Arcmap ...
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1answer
6k views

How to calculate Bearing between two GPS points

The following returns 150 degrees using C# converted from JavaScript Bearing formulas, but Google earth returns 210 degrees for the same values. The broken code is GetBearing() but I've also included ...
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1answer
460 views

RINEX specs and OS library

Is there any OS library to read/write/process RINEX data? I've been wanting to start a OS library to read and write RINEX, which is something I need for a project, but not actually post-process them. ...
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Point interpolation in route

I have a set of GPS coords with X,Y and Course. I need to interpolate additional points based on the course of each point. It would be a simple line intersection based on lines drawn using the 2 ...
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2answers
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Trimble GeoXH, XM, XT - Data logging without Terrasync or GPSCorrect?

Is it possible to capture data for post processing on a Trimble GeoXH, XT, or XM without using Terrasync or GPScorrect? Specifically I would like to create a RINEX file. A Trimble 4000 series receiver ...
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1answer
393 views

How can a single line be computed from multiple possibilities

I have datasets containing continuous GPS streams of data that represent routes or trails. For any given route, I probably have at least 5 (in some cases many more) different sets of data. Given that ...
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1answer
250 views

Calculating Distances between coordinates

I have 75 coordinates in WGS84 that I brought in from an Excel table. They are now on my imagery basemap spanning across about a half mile on either side of a dirt road in Prescott National Forest in ...
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1answer
3k views

What is a .ssf file?

What exactly is a .ssf file? I am refering to the .ssf files used with Trimble GPS units. I am aware that it is some sort of post processing correction file, but I do not know more than that.
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Is there an industry-standard official mapping of GLONASS satellites to “PRN” values?

In the U.S. GPS system, satellites are uniquely identified by the PRN number broadcast by each satellite. This ID is usually visible on most GPS receiver platforms that provide access to individual ...
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1answer
2k views

Is machine learning used much in GIS?

I'm new to GIS. Is machine learning used much in this field, and where? I'm investigating a job opportunity with a mapping company working on traffic awareness. My background is in supervised machine ...
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1answer
422 views

GPS problem in QGIS

I have a very strange problem that I cannot understand. I am trying to put together a demo-laptop with QGIS and gps. On other computers I have it working as expected, but on this particular box ...
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1answer
306 views

Proper work flow to move manholes and pipes to surveyed location

I would like to know how to accomplish the following task using QGIS. I have an existing point shapefile representing sanitary sewer manholes and an existing polyline shapefile representing sanitary ...
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3answers
311 views

How can I add 3 axis orientation information to my photos?

I have a survey project where I need to record not only the location, but the direction (bearing and angle of elevation/depression) that the camera was pointing at the time the picture was taken. ...
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745 views

Calculating “travelled distance” of a GPS track without including “stops”

I have a set of GPS tracks from a cycling event and I want to correlate their distance along the route. Problem is: when a rider stops, generally by entering a covered place, GPS keeps logging (low ...