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Easting and Northing coordinates Google Earth and BaseCamp

Started by wiiawiwb, August 03, 2012, 04:16:57 PM

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wiiawiwb

OBJECTIVE - To create a waypoint in BaseCamp, based upon coordinates from Google Earth, then print out a topo map with that waypoint marked.

PROBLEM -  The waypoint  is not positioned in Basecamp where I would expect it to be.

I am going to bushwhack to a pond from a trail. I have downloaded the NyTopo11 from this website then imported it into BC.

My first step was to go to Google Earth and really zoom in on the pond and create a waypoint on the midpoint of the western shore of the pond.  I wrote down the Easting and Northing coordinates of this waypoint. Then, I went to BaseCamp and created a waypoint and plugged in the exact coordinates. When done, the BC waypoint appears approximately 100`west from the shore of the pond.

My gut tells me that the coordinates from Google Earth are accurate as I zoomed in as far as I could. Why wouldn't the waypoint in BC appear on the pond's edge, as it does in GE, rather than ~100' west from shore?

Boyd

Various things might be happening, but the most simple and likely explanation is that the map you downloaded just isn't that accurate. The USGS water data used by most mapmakers could easily be off by 100 feet from my own experience.

Do you have a subscription to Birdseye? If so, you can download that in basecamp and see the topo map superimposed on top of it. You will then see exactly what the differences are. If you don't have Birdseye, you could make a custom map in Google Earth, then open that in Basecamp and see how it lines up with the topo.

Seldom

Quote from: Boyd on August 03, 2012, 07:04:28 PM
Various things might be happening, but the most simple and likely explanation is that the map you downloaded just isn't that accurate. The USGS water data used by most mapmakers could easily be off by 100 feet from my own experience.
But I've read of similar inaccuracy in GE.  Best way to find out what's right is to go to the waypoint and see if your feet are dry or wet.

babj615

Quote from: Seldom on August 03, 2012, 10:30:38 PM
Best way to find out what's right is to go to the waypoint and see if your feet are dry or wet.

This.

No map is perfect, some less perfect than others.

Water features like this can change dramatically over short periods of time, and are commonly 'off a little' in any map.

Where I live, Google Earth is remarkably always within 10', using a Montana GPSr that at best gets 7' accuracy.

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maps4gps

If you would have obtained the waypoint coordinates from the topo map and then and then created a waypoint in Google Earth would you say GE was incorrect?

Remember that the hydro comes from USGS topo maps many decades old; whereas GE images may be only a few years old.  The width of a line on a 1:24,000 scale printed map is 20'; the pixel size in an image might be 1m or even 1ft (or less) depending on what imagery was available/used. 

The real test, as Seldom mentions, is to occupy the point on the ground.

wiiawiwb

Since I'm new to bushwhacking, I decided I better get some experience before I go to this pond.  I went to a local preserve (~800 acres) that has trails, ponds, and a few small buildings (used by Boys scouts). Before hand, I went to GE and identified trail junctions, one particular pond and a small building. I plugged those coordinates into BC (and my GPS) and then printed out maps.

The forest was thick with blow down, undergrowth and more and was tough to navigate through. I used only my compass and was able to get very close to all four locations when I bushwhacked. I was pleased with that.

I checked each location when I got there and the coordinates taken from GE were dead nuggets. I checked my GPS and it was right on with the map and where I was supposed to be.

Boyd - I do have Birdseye and you're correct. Thanks!

Seldom

Quote from: wiiawiwb on August 05, 2012, 07:53:36 AM
I checked each location when I got there and the coordinates taken from GE were dead nuggets. I checked my GPS and it was right on with the map and where I was supposed to be.
Not familiar with "dead nuggets"; did the GE coordinates agreed with the map?

wiiawiwb


babj615

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Geocaching ID: Atlas Cached
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