GeoChron Blue Holdoff Error - Zoo Elephant Movement Study

GPS/GNSS Development Boards
1

Hi all,

I’m conducting some research on the walking rates and distances of zoo elephants. Ideally, I’ll be able to accurately quantify these measurements and compare them to wild elephant movements. To do so, I need a unit that gives:

High accuracy - an elephant stride is 0.67 - 4.4m

Inexpensive - need sets for as many as 20 institutions; let’s say $150-400/unit

Small in size - needs to fit on an elephant collar or anklet

I’m investigating the feasibility of using GeoChron Blue data loggers (datasheet 2009.1.15) to track this movement. I have three (borrowed) units right now. I am having some problems setting the Holdoff number, and it is unclear whether this number sets “how many instances of the RMC sentence to disregard after the initial lock before taking data and logging it” (per the manual) or “you use the holdoff to specify the logging time intervals, i.e. log the sentences every 1 s” (as in this thread by someone who owns 110 of these units: viewtopic.php?f=17&t=10359&hilit=holdoff).

Specific problems with my unites are:

Unit #1 - the holdoff number will only alternate between 5 and 77, no matter what numbers are inputted (using putty).

Unit #2 - the holdoff number alternates between a few different numbers, such as 5, 23, 33, depending on what numbers you enter.

Unit #3 may be inoperable; the status LED emits only a steady green glow, in standby and run modes. I haven’t tested it with putty yet.

So my questions are:

What are any and all of the effects of the holdoff number?

How can I get my units to accept the holdoff numbers I want?

I’m also looking at the possibility of RFID or bluetooth technology, but have received quotes in the tens of thousands of dollar range for a single unit of the former, meaning GPS or bluetooth will likely be my best options.

Thanks,

Matty

2

Hello,

Lets tackle the issues with the GeoChrons first. The third one sounds like there is an issue with the GPS module. Most commonly it comes down to a pin in the connector being bent and therefore not properly connected. I would check that first.

The other two are rather strange I haven’t heard of such an issue before. I’d recommend trying the reset command first. The holdoff basically tosses the first couple readings after a gps lock is achieved so that when you analyze your data, you don’t have a strange reading at the start of the data when the receiver is still working to get a precise-as-possible reading.

As far as a solution for the project, I’d recommend either this Geochron or the Kinetamap; http://www.sparkfun.com/products/8725 . The Kinetamap incorporates a triple axis accelerometer as well which may be beneficial in analyzing the elephant’s strides. You’re pretty correct with the RFID solution, to able to cover the distances of an elephant enclosure the system would be rather pricey. I’d imagine GPS would be the best.

Thanks,

Pearce