A few days ago we saw how to capture data with the Mobile Mapper 6, now let’s try to do post-processing. This requires to have installed Mobile Mapper Office, in this case I’m using 2.0 version that comes with the purchase.
The most practical way for this is to use Prolink, although if the data are being stored in the external memory, comes out more functional to removing the SD card and take the files from there.
Loading data to Mobile Mapper Office.
I previously explained the functionality of different formats, all data is stored in the .shp files but .map files are layers’ containers, so if files are downloaded to a single folder, just opening the .map we could have all layers that were configured. (As it is done with a .gvp from gvSIG)
To load them in the Mobile Mapper Office, it is selected from the blue button.
If you don’t want to download the project, you can create a new one with the “New” option and then load the layers.
As shown in the top graph, in the left pane you can turn off or on the .shp layers, whereas in the right it can be changed the fill or line color property.
Post-processing of data.
To load data for post-processing, use the Add remote raw data button, with which we can select .grw data that was saved in the GPS. These are reflected in the panel’s bottom, both the initial and final hours.
To load reference data, use the following button, which allows in one hand, load data available, including:
- Raw data in Ashtech format (b *.*)
- RINEX raw data
The other option is to download data from the web, if we have Internet access. Here you can set the number of stations or even the surrounding miles, and then the system starts searching for stations that have available data for those hours when we have captured information.
There is, looking at the ftp RINEX data from the NOAA’s CORS stations, sure that being be in the United States or Spain it would do wonders, because there are more nearby stations serving information on the Internet.
See how when it’s given the option of 7 stations it identifies me the IGS server of San Salvador; I guess that is the CNR placed at 168 kilometers. There also appear two servers in Guatemala and two in Nicaragua, with the difference that those are at 242 and 368 km respectively. All taking data every 30 seconds, it is clear that none of these distances are acceptable for a serious work; it requires data from a more nearby base.
Once you choose which will download, then we select it and press the Download button. There can be seen how in the time scale is matching the data, once this is done we have only to press the Start process button, and wait for the end of treatment.
See this example, is a parking measured four times; the blue lines correspond to a survey using footage every 1 second. The triangles correspond to the real information, taken with a millimetric precision Promark equipment, just in the same period of time.
When performing post-processing, see what happens, this correction sets the object stored in the GIS layer, ie the shape file, modifying its geometry data, but not its tabular data stored in the dbf.
It is interesting that the relative distance without post-processing goes less than a meter, if are taken in equivalent times. But the absolute error goes between 3 and 5 meters, when the post-processing is made this lows less than a meter.
It’s not so bad for equipment that goes down to $ 1,500 (The Mobile Mapper 6); the second example is taken from an exercise downloaded from the Magellan website.