GPS - Drift problem

Projects Networking, Protocols, and Devices
1

Hi. I have a problem with the drift effect, after starting, in fix e.g. 14-16 satellites, it can make a error by 5-6 meters, only after some time in motion, it correctly indicates, is it normal?

2

The reported position tends to stabilise in the short term, a few minutes say, to within 3 to 10M of the actual position.

But the reported position will still move over time.

The GPS does no know its position is in error, not does it know that its drifting around.

3

Hello
you can derive a figure of merit by the analysis of the xxDOP values provided by the GPS receiver.

4

Without differential GPS, the accuracy you're seeing is about as good as it gets.

5

Can you write something more how to do it? Thanks.

6

Hello
Take a look in the world wide net and ask for HDOP, PDOP etc.

7

Your GPS tools may allow you to enable WAAS Wide Area Augmentation System

WAAS may be of some help. And yes, expect some drift but once WAAS is doing the thing there should not be much drift.

8

Do you have a WAAS enabled GPS receiver? Example:

" * DGPS/WAAS/EGNOS supported"

9

Yes, SBAS is on. I still have a question, how to check, for example, using GPGGA (HDOP) the accuracy quality, i.e. the range from 1 to 2?

10

I have used Fire stations and Benchmarks. Fire stations are very accurately orientated and their Lat/Lon measurements are spot on. So far every time I ask the Fire station gives their locations and benchmark locations are, typically, written on the benchmark.

11

Read the output from the GPS manually or use a Library such as TinyGPS++.

12

I mean, how do you convert precision error to meters ? I mean, how do you convert precision error to mertry? or how to determine if the precision is currently very good, good, medium or bad.

13

When I am in the middle of a wilderness area and 3 days in either direction from a road, I use GPS and a map marked with UTM.

14

All explained here;

https://en.wikipedia.org/wiki/Dilution_of_precision_(navigation)

But why are you actually asking, the postition error is only an estimate with some degree of confidence ?

My own experience (when navigating with map and compass) has been that although a GPS might report a postion error of '5M' it could be 30M or so out in actuality.

15

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