[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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>>
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>> >
>> >
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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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