U-gotMe Software

The i-gotU GT-800 (pro)

The i-gotU GT-800 (pro) is a small GPS logger, hardly bigger than an AA battery. It has a 128×128 pixel display offering much information. It is particularly useful for sports. It is based on the Sirf III chip and pretty accurate, see here for a comparison to two other GPS devices. The pro version has in addition to the normal version a atmospheric pressure sensor and a digital compass. Both versions have a acceleration sensor. The device is brought to sleep when it no acceleration is measured.

The i-gotU GT-800 offers a.o. following functionality:

• Logging of your track
• Logging of waypoints at the push of a button
• Following a predefined route, uploaded to the device. It shows the direction to the next route point

U-gotMe offers full access to tracks, routes and waypoints in the device. The way to present the information is via GPX files. GPX is a standard for exchanging GPS information and is used by many computer programs and
can easily be converted.

The i-gotU GT-820 and GT-900 (pro)

Version 2.0 of the software support the GT-820 Pro and the GT-900 Pro. The non-pro versions are not supported yet, since they have another memory map. If someone could provide me with these devices, I can add  support though ;-). Check out this page for a mutual comparison between the GTs

The application

U-gotMe is a utility to download tracks, download waypoints and up/download routes from the i-gotU GT-800/820/900 Pro and save them as GPX files. It is based on igotu2gpx by Michael Hofmann.

The reasons I wrote it:

• I don’t want to use @Trip, I use Oziexplorer and Everytrail for maintaing my trips.
• Though @trip has GPX export facilities, I found it erronous in some occasions
• @trip does not provide all information that is available from the device
• @trip unnecessarily erases the whole device, even if only it is partly full.
• I could not use igotu2gpx: it does not support the i-gotU GT-800. It does not seem to work under Win7 and it does not support comports >COM9 (it will in future)

Limitations:
It might support other types of i-gotU, but I did not test it (in fact it does support the GT-120).

The application, what it is and what it is not

This application just meant to retrieve data from the I-gotU device and make it available for further processing. It does not offer much functionality to maintain your tracks, display your tracks, add photos, adorn tracks, define routes. For this, use other software.

Features

• Download tracks from the device
• Write selected track to GPX file, TCX or CSVfile.
• Track heartrate. Export to TCX or CSV file.
• GPX 1.0 and GPX 1.1 compliant. Click for an GPX 1.0 sample or for a GPX 1.1 sample
• Erase track memory
• Download the waypoints logged by the device and write them to GPX file
• Upload routes from GPX file (e.g. from Oziexplorer or the Waypoint bicycle route planner)
• Supports route point symbols from Oziexplorer
  
• Download routes from the device and write to GPX file
• Read some device info, like serial number, type, etc
• Download device log and save to txt file
• Show speed graph
• Show heartrate graph
• WinXP, Win7, probably other Wins. 32 and 64 bits. Linux
• Supports GT-120, GT-800, GT-800 Pro, GT-820 Pro, GT-900 Pro

Next screen shows the exported track and waypoint imported in Oziexplorer.

Requirements

• i-gotU GT-800 with firmware 6.05, 6.11 or 6.16 or i-gotU GT-800Pro with firmware 7.11 (other versions may work, but I did not test)
• Windows PC or Linux PC
• Java runtime environment
• On Linux: appropriate rights

Other configurations may work, but is not guaranteed

Linux…

Since version 1.1 the software runs fine under Linux. A few steps are prerequisite. Consult the embedded INSTALL_AND_RUN.TXT file for a description how to get the program running (thanx to Arie Peterson, for his support).

Dependencies

• Java SE (tested with Java SE 1.6.0_23)
• date4j library
• RXTX Comm library
• JSSC Comm library
• Pure Java Comm library

During development three java libraries were tested. RXTX is the default. If it gives trouble the other libs can be used.

The I-GotU GT-800

This document describes the serial protocol used to communicate to the i-gotu devices.

GPX

The application supports GPX 1.0 and 1.1. The GPX 1.1 standard no longer supports <speed> and <course> (GPX 1.0 does). Both standards define the <hdop> element, but not <ehpe>, whereas the GT-800 only provides EHPE (see below). Therefore when export to GPX 1.1 is chosen, <ehpe>, <speed> and <course> are added within the <extensions> element. Refer to the GPX site for more information on the format and how to test compliancy. Following GPX elements are exported for track points:

GPX 1.0

longitude

Longitude in degrees

latitude

Latitude in degrees

ele

Elevation in m. On the GT-800 device this is the elevation based on GPS, on the GT-800 pro this is elevation based on atmospheric pressure measurement (more sensitive)

timestamp

Timestamp in UTC/Zulu time

course

Course in degrees (0-360)

speed

Speed in m/s (note: @trip logs in km/h, but this is not according to the specs)

sat

Number of satellites used

GPX 1.1

longitude

Longitude in degrees

latitude

Latitude in degrees

ele

Elevation in m. On the GT-800 device this is the elevation based on GPS, on the GT-800 pro this is elevation based on atmospheric pressure measurement (more sensitive)

timestamp

Timestamp in UTC/Zulu time

sat

Number of satellites used

extensions/course

Course in degrees (0-360)

extensions/speed

Speed in m/s

extensions/ehpe

This is the EHPE in m.

extensions/elegps

Elevation measured by GPS (GT-800 Pro only)

Note on EPHE/HDOP. EHPE stands for ‘Estimated Horizontal Positioning Error’, HDOP for ‘Horizontal Dilution of Precision’.  National Park Service defines:

EPE = HDOP * URA (1-sigma) would give a measure of the 68% confidence circle, i.e., 68% of your position fixes would fall within and 32% would fall outside.

EPE = HDOP * URA (1-sigma) * 2 gives a measure of the 95% confidence circle, i.e., 95% of your position fixes would fall within and 5% would fall outside.

EPE = HDOP * URA (1-sigma) * 0.73 gives a measure of the 50% confidence circle, i.e., 50% of your position fixes would fall within and 50% would fall outside. This is also known in the literature as CEP (Circular Error Probable).

Definitions:

* HDOP – Horizontal Dilution of Precision

* URA – User Range Accuracy is a quantity that is transmitted in the navigation message that is the predicted (not measured) statistical ranging accuracy. Since it is defined for SPS (Standard Positioning Service), it includes SA.

Since we don’t have sigma nro URA we cannot convert.

The GPX files as generated by U-gotMe can be verified using the method described on the GPX site, using the Apache Xerces SaxCount tool. This tool downloads the XSD files form the GPX site and from the U-gotMe site
and verifies the XML structure. For the extensions mentioned above, the XSD file is on the U-gotMe site.

Feedback

I am interested in your experience with the software. Please, send an e-mail to: jorgen at deepocean.net.

License

The software may be used freely for non-commercial purposes. Source code is available on request. Software or code may not be used for commercial puposes without approval of the author.

Disclaimer

Use of the U-gotMe software is at own risk. Maybe it will damage your i-GotU device or result in other unforseen damage. I won’t take responsibility.

Credits

Thanx to the excelent work and reverse engineering by Michael Hofmann.