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Google Earth ruler question

 
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  #1  
Old 08-12-2012, 10:32 PM
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Google Earth ruler question

Hi guys, I've been using Google Earth for a while now and really enjoy it for measuring those shooting distances that my rangefinder won't reach or finding a new shooting position ect. My question is on the ruler: There is a "Map Length" and a "Ground Length." Would the map length basically be my "shoot to distance" taking into account the angle and the ground length my "straight line" distance such as what a standard laser rangefinder would give you without angle corrrection?
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Old 08-12-2012, 10:47 PM
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Re: Google Earth ruler question

At higher elevations, the map scale is slightly off. The "map distance" does not account for the fact that an inch on the map in Leadville is not the same as an inch on the map in San Diego. Ground distance accounts for that. So the ground distance should be closer to your RF reading. I just did a test and the ratio over the Gulf of Mexico was 1.005 map length per ground length. In the Himalayas, it was 0.99 map length per ground length, due to the ~15,000 feet of elevation difference.
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Old 08-12-2012, 11:07 PM
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Re: Google Earth ruler question

Quote:
Originally Posted by NomadPilot View Post
At higher elevations, the map scale is slightly off. The "map distance" does not account for the fact that an inch on the map in Leadville is not the same as an inch on the map in San Diego. Ground distance accounts for that. So the ground distance should be closer to your RF reading. I just did a test and the ratio over the Gulf of Mexico was 1.005 map length per ground length. In the Himalayas, it was 0.99 map length per ground length.
Thank you! So obviously the two different lengths have nothing to do with changes in gravity/shoot to distances based on differences in elevation/angle. Question answered.
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Old 09-24-2014, 02:08 AM
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Re: Google Earth ruler question

I beg to differ with NomadPilot's answer... I've measured multiple locations I'm familiar with where there's significant incline. In some areas it measure 350 Yards of Map Length and 450 Yards of Ground length. Based on those observations I would assert that Map Length is the distance point to point (not accounting for altitude changes), whereas Ground Length is the literal distance point to point (an approximation of what you would get should you measure the distance using a Range finder.

So, if you don't have a elevation compensating range finder but you know where you'll be shooting you can use Google Earth to tell you the Map Length (which is what you should use when attempting to compensate for elevation changes). As elevation over a fixed flight path length the Actual horizontal distance DECREASES. If you doubt it consider shooting 300 yards straight up or down, How much will the bullet drop... zero. Consequently, when shooting with Map Length of 350 and Ground Length of 450 the holdover should be at 350 even though the total bullet travel will be 450 yards.

IMPORTANT NOTE!!! The ratio of Map to Ground IS affected by changing the ELEVATION EXAGERATION (should be se to 1 in order to get an accurate measure).
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Old 09-27-2014, 11:42 AM
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Re: Google Earth ruler question

I have been wondering this myself as where I'll be hunting is rather rugged, but there are some small canyons/valleys to shoot over. However they go up and down rather abruptly therefore I really don't want to know the actual "walking" distance, but rather straight line.

Where is this setting on Google? I swore I've seen it before, must be right in front of me and I'm overlooking it.
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Old 09-28-2014, 04:04 PM
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Re: Google Earth ruler question

Quote:
Originally Posted by Ohio06 View Post
I have been wondering this myself as where I'll be hunting is rather rugged, but there are some small canyons/valleys to shoot over. However they go up and down rather abruptly therefore I really don't want to know the actual "walking" distance, but rather straight line.

Where is this setting on Google? I swore I've seen it before, must be right in front of me and I'm overlooking it.
After you create your measuring line, you can change it from a linear path (absolute) or clamped to ground. By right clicking your saved line, you can bring up properties. Also, you can use the elevation profile to find distance at certain points and also the slope.
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