Garmiin eTrex HC series gps

[georgehogg]

Hi , I have botany survey work to do which will involve finding specific coordinates from which points, measurements will then be made on the ground to find the locations of previously surveyed 1m quadrats.
1. With the above handset can I type in coordinates to points I have not previously marked ,which the handset will then point to and allow me to walk to and pinpoint the exact coordinates. ? How is that done please ?
2. Also are gps coordinates even accurate enough to return to exact points from which ground measurements were made in previous years ? They would need to be accurate to within 5cm or so.
(My own practice is usually to mark the starting point with a wooden post which I find to be far more reliable and simpler )

[Marty_JG]

Garmin do manuals and it can be worth checking the online version as they get updated.

https://static.garmin.com/pumac/eTrexLegendHCx_OwnersManual.pdf

Page 7 talks of creating and editing waypoints, I haven't tried on that model if you can edit the coordinates but it seems you should.

Page 45 of that manual says the GPS accuracy is under 10 meters and the DGPS accuracy is 3 meters (95% of the time).

[jolly47roger]

For most GPS devices, accuracy of less than 3m is unlikely.

For defining points, it is probably easier to make a GPX file of waypoints and upload it to the device.

[china88]

I agree with JollyRoger

GPS receivers can give a 10 figure grid reference ie to an accuracy of 1 m but because of the number of satellites and their positions have an accuracy of 3-10m at best. In summary accuracy is determined by the number of satellites the GPS can see plus other variables.

For question 1, as JRoger suggests, input waypoints into the device. The waypoint is useful in that it will allow you to see that you have arrived at a particular grid reference point or place. on the map.