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

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19
votes
6answers
4k 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 ...
0
votes
1answer
382 views

Accuracy of GPS and HDOP

Given a handheld GPS with an accuracy of roughly 2 meters (verified through field tests) and an observation with an HDOP of 1.2, the accuracy of that one observation should be within 2 meters X 1.2 of ...
2
votes
1answer
92 views

Reaching cm (inch) level elevation precision using drones

A road construction firm needs altitude data of road path before and after the construction and the error should be less than 3 cm (2 inch). Normally, they put a ground station and workers manually ...
2
votes
1answer
233 views

iPhone app to record 3D location information

Does anyone know of an app that would run on an iPhone or iTouch that would record the X,Y and Z information from an external GPS? I am using a Dual XGPS150 Bluetooth receiver. The GPS will record ...
4
votes
1answer
227 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 ...
3
votes
3answers
59 views

What view of sky is required for RTK GPS

When using RTK or differential GPS technologies, considering the Base has a clear unobstructed view, what view of the sky is required to be able to get an accurate fix with the rover when is moving ...
0
votes
0answers
29 views

Python GPS Observation Equations

I've been trying to write some code that will take pseudo-ranges and satellite positions and then compute the observer's position. I've been trying to follow through this book, but the crucial stage ...
1
vote
0answers
9 views

Plotting GPS plot without uploading data

I'm not sure if this is possible or not, but I'm wondering if its possible to plot a GPS dataset without uploading the data first to CartoDB. I've been analysing some data by uploading the postcode ...
1
vote
0answers
14 views

What is the lowest and highest possible pseudo-range?

I am trying to compact the required data that needs to be sent to the server to post-process the receiver's position. To do this, I figured it'd be possible to offset the pseudo-range by a fixed ...
0
votes
1answer
290 views

Field Equipment: Geneq SXBlue II with iPad and ArcGIS Collector app

My company just recently purchased a Geneq SXBlue II GNSS receiver to be pair with an iPad and the Collector for ArcGIS app. I have heard great things about the submeter accuracy of the unit; ...
0
votes
1answer
25 views

Entering Track from Garmin to GIS not getting basemap and orthomap to line up with Track?

I collected a GPS path on a flight and I would like to condense the path to the place where we landed and took pictures (condensed area at base of map; I want to delete the other part of the line). ...
3
votes
1answer
34 views

problem with the import of a gpx file in any program

I have difficulties to import one particular gpx file. I got it via email and it displays some tracks. 10 segments and 5500 waypoints. i tried as follow: QGIS, also with GPSBabel Google Earth ...
0
votes
0answers
16 views

GPS similar locations aggregation

I have a set of GPS locations (long and lat) where there are many similar locations, i.e., the difference between any two locations is less than 1 meter, so these two locations are virtually the same. ...
2
votes
1answer
291 views

How to use OpenLayers Geolocate with the OpenGeo Suite Client SDK?

I’d like to have GPS functionality added to my OpenGeo Suite Client SDK application. From what I understand it should be possible to use the Geolocate control from OpenLayers. Preferably there ...
1
vote
1answer
343 views

Trimble Net R9 Base Station Receiver File Structure

We just installed our new GPS Base Station Net R9 receiver that replaced our old 5700 receiver. The old 5700 used Trimble's GPS Base software, which the new Net R9 does not. My first problem that I ...
2
votes
2answers
349 views

Store GPS trace with timestamps, then interpolate location by time

I'd like to: Load a 1-second interval GPS trace (not GPX) into PostGIS Then query the table at sub-second accuracy (about 5Hz), and get PostGIS to interpolate the location by time. Is this ...
2
votes
0answers
35 views

Find gravity normal by ECEF or GPS coordinate of point

How to find gravity normal by ECEF or GPS coordinate of point? Is it the same as normal to elipsoid? Is this ordinary way to calculate normal to ellipse? I'm not quite sure which altitude is ...
1
vote
2answers
44 views

Why does GPS not give any info before it has a fix?

All GPS devices tell me how much positioning error there is in the fix (e.g. 12 meters). Then why does it not tell me anything before it has a very accurate fix? When a device is looking for its ...
1
vote
1answer
173 views

What is a good, small GPS data logger that stores accuracy information?

I'm looking for a small GPS data logger for geotagging photos, and I've had trouble finding one that meets my requirements: Small, key-fob size would be ideal. It should also store its tracks on ...
0
votes
1answer
30 views

How to set datum in GPS connection setup window in ArcFM Viewer for ArcGIS Engine Application

I have a custom application based on ArcFM Viewer for ArcGIS Engine. I want to use an external GPS receiver with that application and the setup window does not let me choose a different geographic ...
2
votes
0answers
40 views

Time of the gps fix in GPGGA sentence is always rounded

I am using QSTARZ 818XT device for my app. I am using GPGGA sentences to get the GPS fixes, but I have noticed that timings are always rounded like xxxxxx.000 - for 1Hz GPS frequency and xxxxxx.x00 ...
1
vote
0answers
33 views

Average stationary position with GPS

Is it possible to average a stationary position with a GNSS (GPS, GLONASS...) with a centimeter accuracy without an external corrections (like RTK)? If so, how long does such averaging have to take? ...
1
vote
1answer
2k views

GPS Coordinates to WKID 102100

I'm currently creating a project for ios and I'm using the latest ArcGIS IOS api. I have a mapView that is using the spatial reference skid 102100 and i am receiving lat long coordinates from an ...
2
votes
1answer
22 views

Setting elevation data for tie points in Pix4D

I am currently working in Pix4D and am trying to assign elevation data to my selected tie points. I have aerial images taken using a camera with GPS from an aircraft and am working with a fairly ...
1
vote
0answers
76 views

Determining accuracy of coordinates from handheld GPS?

I'm working on a project for class, and I'm mapping GPS on Google Earth with a KMZ file. I used a handheld GPS 24°6.691'N + 74°27.833'W. How accurate is my coordinates? I know I'm in decimal ...
10
votes
10answers
4k views

Need a Benchmark GPS Trajectory data-set? Anyone?

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 ...
1
vote
2answers
401 views

Convert GPS coordinates to EPSG:54004

I need to convert GPS coordinates to EPSG:54004 on android. Are there any libraries or formulas to acomplish the task? Thanks in advance.
0
votes
0answers
36 views

How to create speed maps with gps data

I am looking to create a speed map from gps data, one of the problems is that the data overlaps due that the road is a track. How can be the best way to plot this map? I have Qgis and ArcGIS options ...
1
vote
0answers
15 views

GPRS data receiving in Java

i am creating a java program that will receive data from GPS tracker device and will store it in MySQL. for this purpose i need to create a GPRS connection for receiving data. Can anyone help me how ...
1
vote
0answers
35 views

How can I calculate times with gps data using random points on the track? [closed]

I have GPS data from a car that is circulating all the time in a closed circuit. I need to put a few points along the route, about 3 or 4 and calculate the time it takes to get between points. These ...
1
vote
5answers
2k views

Solutions for uploading maps to GPS (forestry maps: roads, trails, hydro, polygons)?

I'm using a QGIS 2.2.0 Valmiera on a Windows 8.1 system Desktop. I'm a forester and I would like to have a cheap solution to load maps into the handheld Garmin 60, 62 or 64 series GPS. Free would be ...
1
vote
1answer
85 views

GPS tracking times

I have a GPS data on a closed road, where the cars riding laps, and I want to know how long takes to do 1 lap and also I want to add some points to calculate how long takes in specific sections. One ...
16
votes
14answers
5k views

Mobile Data collection options

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 ...
1
vote
1answer
354 views

GNSS planning online vs trimble planning 2.9 software

Why using the same parameters GNSS planning on-line and Planning 2.9 Trimble show me different Dilution of precision (DOP on the graph)?! Which program is better mission planning solution for GNSS ...
1
vote
0answers
36 views

Post-processing GPS Satellite Measurements

I am working on a system that reports its location to a server using very little power. In order to achieve an extremely low power usage, I am avoiding having to download both the almanac and the ...
1
vote
0answers
15 views

Filter GPS tracks to determine “Moving Time”

I am working with GPS tracks of outdoor activities, think cycling, running, hiking. These activities often have "rest periods" where people take a break, wait at traffic lights, or just stopped their ...
3
votes
2answers
162 views

QGIS Real-Time Vector Layer Creation

QGIS is running on my Windows PC. I have a CSV file on my PC that is remotely updated with values of a raspberry pi's GPS position and some wifi-status readings. Is it possible to create a vector ...
1
vote
1answer
215 views

How to compare GPS absolute positioning receiver accuracy

I have two different types of GPS modules which are in absolute positioning mode (pseudorange data) Lets say one of them is attached in microcontroller (such as arduino, rasbpy, etc) and the other ...
16
votes
6answers
2k views

Sources of realtime spatial data

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 ...
29
votes
6answers
2k views

Does an earthquake affect GPS?

There are news reports saying that the Sendai earthquake a couple days ago has shifted the earth on its axis and moved the island 8 feet. Last year, there were similar reports with the earthquake in ...
37
votes
9answers
48k 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 ...
7
votes
2answers
5k views

postprocessing GPS coordinates with RINEX data to improve precision?

Im doing some mapping for OSM in my region and I am curious if the precision of tracks from a GPS Receiver can be improved if they are post processed with RINEX data. The tracking is done with a ...
2
votes
0answers
44 views

Convert xyz coordinates to lon/lat to calculate height change GPS time-series data [duplicate]

How can I convert the XYZ coordinates in Lat, lon to calculate height in metric system? XYZ ascii site YYMMMDD yyyy.yyyy __MJD week d reflon _e0(m) __east(m) ____n0(m) _north(m) u0(m) ____up(m) ...
2
votes
2answers
367 views

In hyperbola model of how GPS equations are solved, why do 3 satellites give only 2 hyperboloids and 4 satellites only 3?

The Hyperbola depiction of how the GPS equations are solved: From several psuedoranges measured at the same time, we can calculate the (absolute) difference in the distances between us and these GPS ...
2
votes
1answer
63 views

Importing xyz text ascii GPS time-series for velocity visualization using QGIS?

How i can import text ascii xyz gps time-series in QGIS for velocity visualization? Example xyz MLBU 07SEP17 2007.7098 -0.119998752351520E+07 0.626106994328102E+07 -0.199557178074915E+06 ...
2
votes
0answers
20 views

Why time differs between gps and ntp exactly 90 seconds

EDIT: This question can be closed due to figured out the problem was in the NTP configuration. While the gps device is no gps data received, gps device is send gps time to server as zeros ...
0
votes
1answer
47 views

Rounding Coordinates

If you want an accuracy of seven digits, should you then round to that value or simply just cut the numbers after that? Example: 51.1936137567 to 51.1936138 or 51.1936137567 to 51.1936137
2
votes
2answers
3k views

What class/types of smartphone chipsets support GPS, A-GPS, GLONASS AND have extended kalman filtering?

I've been testing several Android phones (all running Android 4+) Sony Xperia T, Moto G, Nexus and HTC 1 which are all giving decent tracks (all of which use GPS/GLONASS) However we are also using ...
0
votes
0answers
21 views

Live GPS tracking with both ping script

That's a professional context : During a travel between two train station, I would like to use the live tracking and analyse the network performance (access by Wifi & 3G/4G ). I would like to ...
1
vote
0answers
36 views

Turning QGIS Map into real time GPS for phones?

I'm attempting to create a map in QGIS for use on a website that will allow users to navigate pathways in a park (i.e. choose a desired location, and be shown directions). I'm done with the map ...