[GIS] GPS tracking and Web mapping

google mapsgpshere-mapsopenstreetmaptracking

We are developing a tracking software and we are the stage where we test the reliability of our location stigma on the following web-maps

Google Map
Nokia HERE
Open Street Map (OSM)

We observe that our location appears accurate on Google maps, however when switched to Nokia or Openstreet there is a discrepancy of around 40-50 metres from our actual location.
Most importantly our GPS position accuracy is around 2m.

Could it be inaccuracy of map calibration or any similar problems known by anyone?

Best Answer

If you are using same location (latitude and langitude) on all maps, then there is little possibility of descrepancy due to location. It is possible that the maps have descrepancy among themselves. You can compare accuracy of google and osm map at mapcompare. See if there is any descrepancy.

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[GIS] How to improve positioning of images taken with GPS and Gyro info

Ideally you would post process the GPS against Rinex and other POS (position data including Inertial Measurement Unit and Distance Measurement Information) data - this will refine the GPS accuracy. Where satellite reception drops out the gyro or IMU (inertial measurement unit) steps in to apply 'dead reckoning'. We use something called POSpac that takes the GPS, Rinex, IMU and DMI (distance measurement instrument) information to best position our GPS data, which we can then synchronise with the images.

Google Maps/ArcMap – Working with Lat/Long Coordinates

Due to various vagaries in the ArcGIS software, I'm going to tell you to use different coordinate reference systems. That will let you access the predefined transformations and hopefully make your life easier.

Use WGS_1984_Web_Mercator_Auxiliary_Sphere instead. This one uses WGS 1984 for the geographic CRS (aka datum). The one you're using, WGS_1984_Web_Mercator, uses a sphere (GCS_WGS_1984_Major_Auxiliary_Sphere) and there are no predefined transformations for it.

Next, use Monte_Mario_Italy_1 which is the same, just a different name. Pick Monte_Mario_To_WGS_1984_4 for the transformation.

Or if you want to use Roma_1940_Gauss_Boaga_Ovest, you'll have to define a custom transformation that's a copy of Monte_Mario_To_WGS_1984_4.

FROM roma 1940 TO wgs84
Method: Position Vector
X axis translation: -104.1
Y axis translation: -49.1
Z axis translation: -9.9
X axis rotation: 0.971
Y axis rotation: -2.917
Z axis rotation: 0.714
scale difference: -11.68

If you define a custom transformation in ArcMap, you may have to define it FROM wgs84 TO roma 1940. If so, change the signs on all parameters.

Best Answer

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[GIS] How to improve positioning of images taken with GPS and Gyro info

Google Maps/ArcMap – Working with Lat/Long Coordinates

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