GPS velocity accuracy

[7600onair]

Looking at this GPS sensor: http://www.adafruit.com/products/790
It lists the Velocity Accuracy as 0.1 meters/s, which is very good for a micro sensor.

My project needs still higher accuracy. Are there any aftermarket programs that can correct the data? The manual doesn't discuss the calculation methods... does it use doppler shift calcs?

Thanks,
Nathan

[adafruit_support_bill]

What is the application? If you can sample over a longer distance, your accuracy would improve (GPS Positional accuracy / sampling distance) - assuming straight-line travel.

[7600onair]

I will be datalogging an object moving in random circles. In this case, including position would add to the error. Wanting to measure max velocity over the datalogging period.

Thank you for the response.

[adafruit_support_bill]

GPS velocity calculations are always going to be limited by the positional accuracy.
You might be better off using a combination of accelerometers & gyros. We have triple-axis versions of each:
https://www.adafruit.com/products/1032
https://www.adafruit.com/products/163
https://www.adafruit.com/products/1120

[7600onair]

Searched the GPS module datasheet. They list Velocity Accuracy as "Without aid : 0.1m/s, DGPS(SBAS(WAAS,EGNOS,MSAS,GAGAN)):0.05m/s"

Since DGPS mode is default, it would be helpful to update your product page to match. It also looks like Position Accuracy is different than listed on your product page.

[tastewar]

Been a while since I played with some of this stuff, but Differential GPS isn't always available, and requires some separate ground reference. Unless you know you're in an area served by one of the services mentioned, I wouldn't count on it. Of course, all of this could have changed in the last 10 years...

[7600onair]

I emailed the GPS manufacturer with this question:
With the embedded data logger function of this unit: http://www.adafruit.com/datasheets/Glob ... et-V0A.pdf
Can the module be re-flashed to store a fix every 1 second instead of 15 seconds?

This is the response I got:
Hi Nathan,

Please post your question on forums.adafruit.com and there is a technical support team will help you!

Thank you!

Regards
Alison

GlobalTop Inc.
No.16, Nan-ke 9th Rd., Science-based Industrial Park, Tainan 741, Taiwan

Note- They sell an USB evaluation board and have software that appears to allow for different modes, one of which may allow for 1 Hz resolution. I was wondering if it can be purchased pre-configured this way.

[7600onair]

Been a while since I played with some of this stuff, but Differential GPS isn't always available, and requires some separate ground reference. Unless you know you're in an area served by one of the services mentioned, I wouldn't count on it. Of course, all of this could have changed in the last 10 years...

tastewar,
I'm not familiar with all the DGPS modes, but WAAS coverage in the US is very good. It may not be everywhere, but the most populated areas are definetely covered.

[adafruit_support_bill]

We get these modules pre-flashed to our specs from the factory. We do not have the capability to modify or re-flash the firmware here. If you do need that capability, the USB eval board may be the best solution for you.