[teqc] Converting Android GPS data to Rinex file format

Lalitha myracacc at gmail.com
Wed Oct 13 15:42:23 MDT 2010


Thanks to everyone for the in depth explanation.

On Wed, Oct 13, 2010 at 12:44 PM, Gerald Creager <gerry.creager at tamu.edu>wrote:

> While there are some types of post-processing that can be achieved with
> latitude, longitude and elipsoid height, such as long-term averaging, these
> will not yield the same degree of success a least-squares approximation of
> position. In general, as indicated earlier, pseudorange, pseudorange-rate,
> precise timing information, precise ephemeris information and spacecraft
> health go into the more rigorous postprocessing methods.
>
> It looks like the Android only provides latitude, longitude, height, speed
> over ground, and heading ($GPRMC) data from the VERY brief review I've done
> (others can correct me). $GPGST might be of some use (I've never seen it
> output by a consumer-grade receiver, though) but I believe it's just noise
> data and not real pseudorange data.
>
> In other words, while you can experiment with some form of post-processing,
> it doesn't look promising.
>
> gerry
>
> Lalitha wrote:
>
>> Thanks Jim for the clear reply. Finally one more question.
>> Is there any other methods to achieve post processing dgps corrections
>> other than converting to Rinex format.
>> I understand from all of your replies that the underlying raw gps data is
>> must for doing corrections with the base station gps data.
>> But still, want to give a try asking if there is any other ways to do it.
>>
>> Thanks,
>> Lalitha.
>>
>> On Wed, Oct 13, 2010 at 10:44 AM, James Johnson <jjohnson at ucar.edu<mailto:
>> jjohnson at ucar.edu>> wrote:
>>
>>    Hi Lalitha,
>>
>>    It is not possible to generate RINEX from an android phone.  This is
>>    because the raw data required for RINEX is not exposed by the
>>    Android API.  You can get some information about the SVs tracked and
>>    a position, but you can not get the raw Pseudo range data.  The NMEA
>>    strings are not useful for generating RINEX as well, simply because
>>    the data is not there.
>>
>>    Sorry for the sad news.
>>
>>    Best Regards,
>>    Jim Johnson
>>    On Oct 13, 2010, at 11:40 AM, Lalitha wrote:
>>
>>     > Hi Homan,
>>     >
>>     > Tons of thanks for the detailed reply. I've been searching the
>>    net and posting in all the android, gps forums for the past 10 days
>>    and didn't get any response till now. Thanks to teqc mailing list.
>>     >
>>     > Q1. I checked the android api for the gps data. It provides GPS
>>    Satellite info from which we can get elevation, PRN (pseudo-random
>>    number), snr, Almanac, ephemeris data etc.
>>     >      Ref :
>>    http://developer.android.com/reference/android/location/GpsStatus.html
>>     > With these data, will it be possible to generate Rinex file
>>    directly from android app?.
>>     >
>>     > Q2. Also, there is a nmealistener provided in the android api
>>    using which we can capture gps nmea strings. Will this data be
>>    useful by anyway to translate to rinex format? (Though, I coudnt
>>    succeed capturing nmea string using my htc magic phone, I can try
>>    with some other phones if this data will be  useful for post
>>    processing).
>>     >
>>     > Thanks,
>>     > Lalitha.
>>     >
>>     > On Wed, Oct 13, 2010 at 9:58 AM, Homan, Thomas
>>    <thoman at co.gila.az.us <mailto:thoman at co.gila.az.us>> wrote:
>>     > Lalitha,
>>     >
>>     >
>>     > .gpx files cannot be converted to Rinex as they don’t contain the
>>    necessary data elements. If I remember correctly, the api only
>>    outputs the final latitude and longitude values. I don’t believe the
>>    underlying raw gps data is accessible but I’m just getting started
>>    on Exclipse.
>>     >
>>     >
>>     > To generate a Rinex file you need to have access to underlying
>>    information such as pseudorange, carrier phase and other data from
>>    each satellite in the GPS constellation. As an example, below are a
>>    .gpx file compared to a Rinex file that I collected in 2005. Each of
>>    the 7 satellites visible has a set of 7 data elements logged out of
>>    my $$$ survey grade receiver and this happens each logging period.
>>     >
>>     >
>>     > Peruse the api docs and see if there is access to the underlying
>>    data and not the final coordinates. If not, then you might be out of
>>    luck. One thing you might explore is if the android OS supports
>>    inserting DGPS correctors so you could get real time sub-meter
>>    accuracies.
>>     >
>>     >
>>     > Hope this helps some.
>>     >
>>     >
>>     > Tom
>>     >
>>     >
>>     > GPX
>>     >
>>     > <?xml version="1.0" encoding="ISO-8859-1"?>
>>     >
>>     > <gpx xmlns="http://www.topografix.com/GPX/1/1"
>>    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="1.1"
>>    creator="Doug Forster's map viewer"
>>    xsi:schemaLocation="http://www.topografix.com/GPX/1/1
>>    http://www.topografix.com/GPX/1/1/gpx.xsd">
>>     >
>>     > <wpt lat="-42.48781" lon="172.29404">
>>     >
>>     > <ele>1273</ele>
>>     >
>>     > <name>NwDvls</name>
>>     >
>>     > <cmt> 30/01/10 19:14</cmt>
>>     >
>>     > <desc>New Devils Den Biv</desc>
>>     >
>>     > <sym>Anchor</sym>
>>     >
>>     > <extensions>
>>     >
>>     > <type xmlns="Freshmap">Place</type>
>>     >
>>     > <TrackColor xmlns="Freshmap">0</TrackColor>
>>     >
>>     > <FontSize xmlns="Freshmap">90</FontSize>
>>     >
>>     > <GPSColor xmlns="Freshmap">14</GPSColor>
>>     >
>>     > <Layout xmlns="Freshmap">5</Layout>
>>     >
>>     > </extensions>
>>     >
>>     > </wpt>
>>     >
>>     > </gpx>
>>     >
>>     >
>>     > Rinex
>>     >
>>     > 05 10 12 14 44 45.0000000  0  7G 1G24G23G20G16G25G11
>>     >
>>     >   18540407.76711  14441990.35651  22140106.912    22140108.9425
>>  22140103.6715
>>     >
>>     >      -1502.342       -1170.656
>>     >
>>     >   18405511.80411  14342294.04151  23619878.513    23619880.7005
>>  23619875.3565
>>     >
>>     >        382.895         298.360
>>     >
>>     >   18279304.44211  14260112.94351  22317896.240    22317897.3485
>>  22317888.9405
>>     >
>>     >       2122.449        1653.856
>>     >
>>     >   18331079.75811  14289623.90551  20672596.529    20672597.6675
>>  20672590.3895
>>     >
>>     >       1386.704        1080.549
>>     >
>>     >   18282886.39611  14256935.72751  21779940.978    21779941.1535
>>  21779934.4995
>>     >
>>     >       2177.108        1696.448
>>     >
>>     >   18595837.79911  14470056.42251  21824971.770    21824972.4395
>>  21824966.6485
>>     >
>>     >      -2263.324       -1763.629
>>     >
>>     >   18612482.40511  14492926.57751  23828871.571    23828874.4325
>>  23828869.0685
>>     >
>>     >      -2470.753       -1925.262
>>     >
>>     >
>>     > From: teqc-bounces at ls.unavco.org
>>    <mailto:teqc-bounces at ls.unavco.org>
>>    [mailto:teqc-bounces at ls.unavco.org
>>    <mailto:teqc-bounces at ls.unavco.org>] On Behalf Of Lalitha
>>     > Sent: Wednesday, October 13, 2010 9:03 AM
>>     > To: teqc at ls.unavco.org <mailto:teqc at ls.unavco.org>;
>>    gpstech at ls.unavco.org <mailto:gpstech at ls.unavco.org>
>>
>>     > Subject: [teqc] Converting Android GPS data to Rinex file format
>>     >
>>     >
>>     > Hi,
>>     >
>>     > How do i convert the gps data I get from Android GPS Receiver
>>    into Rinex file format in order to do Post processing corrections.
>>     > I can write the gps data into .gpx format using the android api
>>    provided. I use HTC Magic phone with 2.2 api version.
>>     > I cudnt find option for android in the teqc toolkit. Can anyone
>>    help how do I convert to Rinex?
>>     > Also I'm looking for the post processing softwares or service
>>    available for evaluation. I could find only one free evaluation
>>    software 'PPro2' from Kinematic GPS.
>>     > Is there any other free post processing software present?
>>     >
>>     > Thanks,
>>     > Lalitha.
>>     >
>>     >
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>
> --
> Gerry Creager -- gerry.creager at tamu.edu
> Texas Mesonet -- AATLT, Texas A&M University
> Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.862.3983
> Office: 1700 Research Parkway Ste 160, TAMU, College Station, TX 77843
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