Help please ... wrong co-ordinates

[Cameron Corner]

Hi

Very new to this forum and geocaching. We purchased an Oregon 550 which we received during the week.

We took a way point at the post office in town here today and when I looked up the co-ordinates on Google Earth it has us about half a km away (as the crow flies).

Any ideas on what might be wrong?

Thanks in anticipation.

Michelle

edited to fix spelling error in title.

[Map Monkey]

Welcome CC.

Just a couple questions....how did you check the Waypoint on Google Earth? Using the GPX file downloaded from the GPSr or did you read off the coordinates from the GPSr and enter that into GE manually?

If it was the later, two issues appear most times:

- Datum may be incorrect and the coordinates will display ~200m out. Use WGS84 for the Datum.
- Lack of time required for an accurate fix. Some people turn the unit on and expect a 3-4m accuracy within seconds. Multipath and other errors may change this when first turning on.

Hope that helps.

mm

[Cameron Corner]

Thanks so much for your reply MM and the welcome.

I just checked the co-ords by viewing the co-ords on the gps and then manually lining those numbers up with Google Earth (down the bottom of the map screen).

Ok, showing my total newbie status here. How do I do the Datum thing for WGS84?

I think we were there for long enough but if we can will try again tomorrow and make sure we leave it for longer. How long is a good time or is there a way to know that your co-ords have come through correctly?

Thanks for your help ... sorry about the extra questions.

Michelle

[riblit]

Google Earth can be out, so its worthwhile keeping that for consideration.
I think the Oregon 550 has the same menu tree as the 300 so:

On your GPSr touch setup -> down arrow -> position format and read the map datum, it should be set to WGS84. If its not, tap it and change.


You can connect the GPSr to a USB port and have Google Earth download and display tracks and waypoints. Also, you can type coordinates into the Google Earth search box (Fly to) and have Google Earth go to those coordinates.

[CraigRat]

Also notE: if you change the datum, you will have to go get the waypoint again, as the unit converts the old co-ords to the new co-ords, and will still be 250m out!

[Map Monkey]

Also notE: if you change the datum, you will have to go get the waypoint again, as the unit converts the old co-ords to the new co-ords, and will still be 250m out!

Not necessary....all data is stored in Lat/Long, WGS84, DDD.DDDDD format so all you are changing is what is displayed.

With the time issue, this is normally only appearing with a first start-up or not being used for some time (simplistic explanation). Waiting 1 minute with a good view of the sky is normally sufficent to gain a good fix. You can look at the GPS accuracy (a somewhat arbitary number) by touching the satellite bar (the ascending bar graph) at the bottom of the menu screen. Image from the Oregon Wiki page:



The other issue (there are several without seeing how you did it ) is to make sure the coordinate format is the same across both devices (GPSr and PC) when manually copying numbers. The standard position format is DD MM.MMM ("decimal minutes") for Geocaching, so you may need to change this in the GPSR (in the same area as Riblit described before) and make sure Google Earth is displaying this (under options iirc). This is not really an issue when transferring GPX files and/or working digitally with coordinates.

Hope that helps

mm

[Cameron Corner]

Thanks everyone for your help. I've learnt a few things from this exercise.

I've been playing with it this morning. I left the GPS our in the backyard for a good half hour (I forgot about it) and when I checked the co-ords with GE, it was on the money. So, later we will take it back to the PO and try another reading.

Will let you know how we go.

Cheers
Michelle