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Author Topic: Free Digital USGS Quads for Every State  (Read 3737 times)  Share 

Offline jeffblaylock

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Free Digital USGS Quads for Every State
« on: March 28, 2009, 01:32:05 PM »
Jackpot!

While searching for USGS quads for my upcoming trip to Colorado, I stumbled across an online archive of every 1:24K and 1:100K quad, available for free download:

The Libre Map Project

The only catch is, the maps are collarless, which means you can't look at one of them an know the adjacent quads by name. Instead, you have to may wish to search by their grid designation. This could be troublesome, until you crack the code.

AAOOOxY

AA=degrees latitude North
OOO=degrees longitude West
x=row
Y=column

For every 1 degree (AAOOO), there are 64 7.5-minute quads arranged like this:

h8 h7 h6 h5 h4 h3 h2 h1
g8 g7 g6 g5 g4 g3 g2 g1
f8 f7 f6 f5 f4 f3 f2 f1
e8 e7 e6 e5 e4 e3 e2 e1
d8 d7 d6 d5 d4 d3 d2 d1
c8 c7 c6 c5 c4 c3 c2 c1
b8 b7 b6 b5 b4 b3 b2 b1
a8 a7 a6 a5 a4 a3 a2 a1


So, if you know the coordinates, you can search for the quad code. If you don't know that, search by name for the most prominent topographic feature and then use your browser's search function to find adjacent quads.

For example, I wanted maps for Rocky Mountain National Park. It's most prominent feature is Long's Peak, which happens to have a quad named after it. It's 40105c5, meaning the quad is located in the degree set of 40 degrees north, 105 degrees west, at position c5. So the other quads I need are:

40105e7 40105e6 40105e5
40105d7 40105d6 40105d5
40105c7 40105c6 Longs Peak
40105b7 40105b6 40105b5


That's all the quads for Rocky Mountain National Park.

Anyway, a great resource for do-it-yourself topos.
« Last Edit: March 28, 2009, 11:19:13 PM by jeffblaylock »
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Jeff Blaylock
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"We'll be back, someday soon. We will return, someday, and when we do the gritty
splendor and the complicated grandeur of Big Bend will still be here. Waiting for us."--Ed Abbey

Offline badknees

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Re: Free Digital USGS Quads for Every State
« Reply #1 on: March 28, 2009, 02:10:11 PM »
Try this one too. Topos + much more

http://seamless.usgs.gov/index.php
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Offline Casa Grande

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Re: Free Digital USGS Quads for Every State
« Reply #2 on: March 28, 2009, 04:53:38 PM »
that's amazing, jeff...thanks for cracking the Code!
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Offline alcap

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Re: Free Digital USGS Quads for Every State
« Reply #3 on: March 28, 2009, 09:54:45 PM »
Very cool  :eusa_dance:

I've been looking for something like this.
Thanks for sharing it!
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Offline fartymarty

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Re: Free Digital USGS Quads for Every State
« Reply #4 on: March 28, 2009, 10:48:34 PM »


    I must be doing something wrong ..err I mean right...or I'm not understanding your point.
I only tried a few, but every one I looked at had a full collar with the 8 adjacent maps noted about it. Color me very grateful, but confused?  :eusa_eh:  I'll keep a copy of your code breaking in case I ever get smart enough to realize what I need it for.  :eusa_think:

   anyway, THANKS JEFF!
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Offline jeffblaylock

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Re: Free Digital USGS Quads for Every State
« Reply #5 on: March 28, 2009, 10:59:06 PM »
Quote from: fartymarty on March 28, 2009, 10:48:34 PM


    I must be doing something wrong ..err I mean right...or I'm not understanding your point.
I only tried a few, but every one I looked at had a full collar with the 8 adjacent maps noted about it. Color me very grateful, but confused?  :eusa_eh:  I'll keep a copy of your code breaking in case I ever get smart enough to realize what I need it for.  :eusa_think:

   anyway, THANKS JEFF!

Could depend on the state. I only looked at Idaho, Nevada, and Arizona. Or could depend on the program used to view them. Or if you have your program set to turn off the margins. It is definitely easier if you can see the collar.
« Last Edit: March 28, 2009, 11:15:47 PM by jeffblaylock »
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"We'll be back, someday soon. We will return, someday, and when we do the gritty
splendor and the complicated grandeur of Big Bend will still be here. Waiting for us."--Ed Abbey

Offline fartymarty

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Re: Free Digital USGS Quads for Every State
« Reply #6 on: March 29, 2009, 02:51:46 AM »
Quote from: jeffblaylock on March 28, 2009, 10:59:06 PM
Or if you have your program set to turn off the margins.

       :rolling: That's funny Jeff. So while the rest of us don't even know how to turn off our margins, you cerebral hiker types  :eusa_think: can come up with a complex work around that we didn't even know was needed yet. :huh:  :icon_lol:

  Getting back to the code it looks to me that the grid is northwest of the Lat/Long. If so, using 40n 105w, the four surrounding quads would be 40105a1, 39105h1, 39104h8, and 40104a8.  Right?

There's a puzzle/game here somewhere......hhhmmm...I know, using 104 44 30 W,  40 36 10 N, name the containing Quad code and the 8 surrounding Quad codes.  The first poster with the correct answer (no edits allowed, repost if needed) gets an email from Jeff of a picture of Chisos (the dog) (Ok Jeff?). Extra credit if you know the significance of those coordinates. (Hint: Google Earth won't be much help.)
Sudoku? Bah! who needs it! We've got QUADCO. :eusa_dance:
« Last Edit: March 29, 2009, 03:08:41 AM by fartymarty »
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Offline Al

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Re: Free Digital USGS Quads for Every State
« Reply #7 on: March 29, 2009, 03:41:06 AM »
If you are relatively simple like me, download the TIFF version of the topo.

Al
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Offline mule ears

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Re: Free Digital USGS Quads for Every State
« Reply #8 on: March 29, 2009, 08:29:20 AM »
Quote from: Al on March 29, 2009, 03:41:06 AM
If you are relatively simple like me, download the TIFF version of the topo.

Al


I just downloaded the Emory Peak quad in TIFF came in with collars) as a test and it is awesome, including the ability to draw routes etc on the maps! Thanks Jeff!
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Offline RichardM

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Re: Free Digital USGS Quads for Every State
« Reply #9 on: November 06, 2009, 10:28:13 AM »
This site has links to usgs.gov maps in zipped PDF format:
http://www.pickatrail.com/sun/b/america/topo_map/big_bend_national_park/map.html
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Offline badknees

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Re: Free Digital USGS Quads for Every State
« Reply #10 on: November 06, 2009, 11:57:33 AM »
Quote from: RichardM on November 06, 2009, 10:28:13 AM
This site has links to usgs.gov maps in zipped PDF format:
http://www.pickatrail.com/sun/b/america/topo_map/big_bend_national_park/map.html

If you download the plug-in, these maps are geo-referenced
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