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How Do I Find Ground Zero For My Town


halffast

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I have micro's in the middle of town and regular caches out of town.Using my zip code to search nearest caches the nearest is the one I placed about 5 miles to the north east of town.The one I have right in the middle of town says its 4.3 miles south west.

How can I find ground zero for my town.I think it would be a great place for a new cache.

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Using your GPS, no matter what make, probably isn't the way to go because it may figure the location of ground zero differently than Groundspeak. On the Groundspeak home page, select "My Account" on the left hand menu. From the next screen select "Update home coordinates" on the right menu. On the next screen enter the ZIP code in the "Postal Code Lookup" box and select "locate" and you will see the coordinates for ground zero of the city in question in the boxes above. Copy this waypoint down and DO NOT select "mark as my home coordinates" unless you want all your future distance calculations measured from that waypoint! Use the back arrow a few times to get out of that screen and back to the home page or close without saving.

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That would asume only one Zip or Postal code per city. I live in a smallish city and it has several Zips.

 

You could map it out - find several caches and do the proximity thing.

 

For example, 60544 gave me these results:

31a5f50b-d115-42fb-a201-6a9200ddffba.jpg

 

I plotted them on a map, and then did a radius that matched the radial search. It's not exact, but it's darn close.

 

d119ba89-68a5-40e8-ade6-82b09b473927.jpg

 

If your town has multiple zipcodes, it would work the same with doing it for each of the zip codes.

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That would asume only one Zip or Postal code per city. I live in a smallish city and it has several Zips.

I plotted them on a map, and then did a radius that matched the radial search. It's not exact, but it's darn close.

 

I used that zip code with one of the methods above and got an exact number. N41 36.948 W088 11.904

 

How close to that are your coords?

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Some interesting theories here on how to find ground zero (GZ) but some don't hold up. Having done several GZ caches I can tell you that some of the GZs are in the woods where there has never been a road, a house, or a mile marker.

 

Markwell's mechanical method does work and I did something similar on my first GZ cache. Instead of drawing circles I used a "guess" as to about where the GZ was then looked how the distances from that point agreed with the distances Groundspeak used from the town's ZIP code to several caches. By a series of guesses I fine-tuned the distance readings to agree with the Groundspeak list and be within about 50-100 feet of the coordinates I measured at the cache.

 

What you should notice from Markwell's method and my "guess" method is that they both try to agree with the figure Groundspeak uses, not some other imaginary point like a mile marker. However both methods are somewhat inexact and won't get you to the exact GZ. If you want to get to the GZ of a listed cache on Groundspeak then using the method I mentioned in post #5 will give you the correct answer, the other methods are likely to give DNFs.

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Every city has an official Mile Marker 0 (zero) from which all official distances are measured. This is typically 'downtown' at or near the courthouse/city hall and such locations. If the present day locations of the facilities which house these functions have been relocated, this marker location does not move with them. The historical 'city center' for these measurements remains unchanged and essentially never moves.

 

Some interesting theories here on how to find ground zero (GZ) but some don't hold up. Having done several GZ caches I can tell you that some of the GZs are in the woods where there has never been a road, a house, or a mile marker.

 

 

I agree with Team Cotati on this as I have actually seen one of these markers. It was in Memphis, Tennessee and the guide that pointed it out said basically the same thing that Tean Cotati said. These are the "official" Ground zeros in a town.

 

If I understand it right I think the op is wanting to know what ground zero is on this website. If that is the case then the op has several good suggestions already in this thread.

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I used that zip code with one of the methods above and got an exact number. N41 36.948 W088 11.904

 

How close to that are your coords?

 

Not bad. Below is a close-up of the plot of the radius of the four closest caches to the zip code 60544. The red dot is the set of coords that you gave. The green, blue, purple and lavendar lines are the radius of the four caches, with the orange area as the points that would work. Notice that the red dot is indeed within the acceptable boundary of possible points, and the farthest possible point is only 146 meters from the coordinates you gave.

 

5bf22363-34d3-4d04-877b-a6e2539a4de3.jpg

 

The problem is in the resolution that Geocaching.com gives for a distance to a cache. Those distances on the search result page are 0.9 miles, 1 mile, 1.2 miles and I went to another cache of mine and got 2 miles. The problem is that 2 miles can be 1.950 miles or 2.049 miles, which are about 52 feet off. So considering those measurements are ±26 feet, I'd say getting within 146 feet just by maps is not too bad.

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I don't know which GZ you are referring to but the official center of cities and towns in the United

States is not in the middle of any woods. Perhaps if we could agree upon what "ground zero for my town" meant it would do wonders for better communication on the subject. In my mind, "for my town" does not communicate the presumption that the OP is intending to look in the woods.

If you check all of the GZ caches you will find they use the same method which is not the center of town. Here is a quote from the listing for "Ground Zero -Bartlett"
Like many other ground zero caches this one is located at the baseline coordinates Geocaching.com uses to measure distances to caches in the Bartlett area. Before you begin your search you will have to determine what the baseline coordinates are. There is an easy way and there is a hard way to make this determination. There are many routes to this cache. All involve bushwhacking. The bushwhacking may be rough in spots depending on the route chosen. You may encounter some hiking trails, woods roads or snowmobile trails that may help.

 

I agree the center of town may be far different than GZ but if the OP means to place a GZ cache that is the same as all the other GZ caches on the site, I believe you'll find the method I described will give the right answer. Please check some of the GZ caches out and see.

Edited by rjb43nh
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The problem is in the resolution that Geocaching.com gives for a distance to a cache. Those distances on the search result page are 0.9 miles, 1 mile, 1.2 miles and I went to another cache of mine and got 2 miles. The problem is that 2 miles can be 1.950 miles or 2.049 miles, which are about 52 feet off. So considering those measurements are ±26 feet, I'd say getting within 146 feet just by maps is not too bad.

This is an interesting problem. When I was doing the centroid calculations, I also wrote myself a little solver that will find a point given at least three other points and distances from them. I wrote it to do a least-squares estimate of the position, so it will work for any number of points.

 

So the question is this: given a query with some number of caches and their distances to a precision of 500 feet (0.1 mile), how many would it take to get a good estimate of the center point? I am guessing that you would likely do pretty well with 10 or so, though with 100 you could more or less guarantee it would be within 50 feet.

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I always thought the origin of any search performed for a zip code was from the post office for that zip code....

 

that seems to work, at least where I live. The post office truly is roughly 0.40 miles SE from the closest cache listed in the zip code search, 45211.

Edited by 4leafclover
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I always thought the origin of any search performed for a zip code was from the post office for that zip code....

 

that seems to work, at least where I live. The post office truly is roughly 0.40 miles SE from the closest cache listed in the zip code search, 45211.

That method used to work for my town, also. However, they moved the main post office some time ago.

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Gee, I really hope that nothing serious has befallen the OP. :):P

I was waiting for an email stating a reply had been posted and still have not gotten one.Alot of good suggestions though.I am now .9 miles from ground zero and have been talking to some land owners about how to get access to the hill which I think might be GZ.It is 4 miles outside the city limits and might be on DNR land.

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Using your GPS, no matter what make, probably isn't the way to go because it may figure the location of ground zero differently than Groundspeak. On the Groundspeak home page, select "My Account" on the left hand menu. From the next screen select "Update home coordinates" on the right menu. On the next screen enter the ZIP code in the "Postal Code Lookup" box and select "locate" and you will see the coordinates for ground zero of the city in question in the boxes above. Copy this waypoint down and DO NOT select "mark as my home coordinates" unless you want all your future distance calculations measured from that waypoint! Use the back arrow a few times to get out of that screen and back to the home page or close without saving.

This suggestion has given me new coords to check.From the map it is in the area of the hill I am certain it is on.I will check it out.

Thanks for all the help.....My wife says I am obsessed but I dont think I am. :P

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Spent most of the morning talking to land owners near GZ.I was 2 1/2 blocks from GZ but the guy wouldnt let me walk through his land.He thinks that GZ might be on the border of his land & DNR land.Its still possible it is on DNR I just have to find access to it.I will speak to DNR to see if their land comes to the hwy.

Real depressing morning. :lol:

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