Getting Map Coordinates from a Historical Topo Map for use with a GPS

Getting Map Coordinates from a Historical Topo Map for use with a GPS

or How to determine the latitude and longitude on a USGS Topo Map

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Battle Of Bushy Run Pennsylvania

You have a CD of scanned Historical Topo maps. Maybe it's a paper topo map.
Whatever you have at some point you are going to need to get coordinates off of it. It
may be a old long gone house site, or an old park site now covered by woods. How do
you get the site coordinates off of the map to punch into your GPS and go to the site?
Well, that is the purpose of this page, because you see I had the same problem. I had a
treasure trove of maps which contained hundreds of possible metal detecting sites.
I could get to the general area by eyeballing the map, but I wanted something a little
more accurate. So I did a Google search and came across this site:
http://www.lib.clemson.edu/GovDocs/maps/latlong.htm that outlined the steps needed.
I will outline the steps I used and add map images to help. Note that the results will
not be 100% dead on, but will get you close.

STEP 1: To start you will need a print of your map and a ruler that can measure centimeters.

You can use a original topographical map or one you print yourself.

STEP 2: Calculating Longitude

1.Look at the right side (upper or lower corner) under the map name, or the
second of two numbers separated by "x", to find the width scale (longitude) of
the map:
If "7.5 Minute Series" enter 450
If "15 Minute Series" enter 900
If "15x30 Minute Series" enter 900 _________________ See Image Item 1
If the map does not have this you can aslo tell by the scale.
1:24000= 7.5 minute

1:62,500 = 15 minute

2.Using a ruler, measure the width of your map east to west (Exclude the
borders) __________________cm See Image Item 2
Latitude and Longitude are often defined in degrees, minutes, and seconds. There are
60 seconds in a minute and 60 minutes in a degree. The symbols are as follows

3.Divide the #1 by #2 to the nearest whole number ________________cm/sec
° = degrees
' = minutes
" = seconds

4.Enter the Longitude located in the lower right hand corner ______________° ' "

See Image Item 4

5.Using a ruler, measure (cm) from your site, straight across to the right hand
side of the map. _________________ cm See Image Item 5

6.Multiply #5 by #3 (to the nearest whole number) __________________

7.Convert #6 to minutes and seconds by dividing by 60. Your whole number after
division is the number of minutes, and the remainder is the number of seconds.
(Do not use a calculator) For example, 215 can be divided by 60 three times.
215-180=35. So 215 converts to 3'35". ___________________

8.Add #4 to #7

___________________ The answer to #8 is the Longitude of your site.

STEP 3: Calculating Latitude

9.Look at the right side (upper or lower corner) under the map name, or the
second of two numbers separated by "x", to find the width scale (longitude) of
the map:
If "7.5 Minute Series" enter 450
If "15 Minute Series" enter 900
If "15x30 Minute Series" enter 900 _________________

10.Using a ruler, measure the length of your map north to south (Exclude the
borders) __________________cm

See Image Item 10 For a partial printout of a map, measure one full section and multiply.
For example, in the sample 1:62,500 scale map shown, only one full vertical
section is shown. To get the full map size as needed, measure the top to bottom
length of a full 5 minute section and multiply by 3. (3 x 5min = 15 minute or 1:62,500 scale map)

11.Divide the #9 by #10 to the nearest whole number ________________cm/sec

12.Enter the Latitude located in the lower right hand corner ______________° ' "

See Image Item 4

13.Using a ruler, measure (cm) from your site, straight down to the bottom of the
map. _________________ cm See Image Item 13

14.Multiply #11 by #13 (to the nearest whole number) __________________

15.Convert #14 to minutes and seconds by dividing by 60. Your whole number
after division is the number of minutes, and the remainder is the number of
seconds. (Do not use a calculator) For example, 215 can be divided by 60 three
times. 215-180=35. So 215 converts to 3'35". ___________________

16.Add #15 to #12

___________________ The answer for #16 is the Latitude of your site.

Partial 1:62,500 scale USGS Topographical Map Shown

One final note: make sure when entering the map coordinates into your GPS that you
match the datum from the map to the one in the GPS. Also, make sure you get a 3D fix
when you are out in the field.

Test the results of your calculations here:
http://www.topozone.com/viewmaps.asp

If you need to Translate Coordinates:
http://www.jeeep.com/details/coord/

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		Battle Of Bushy Run Pennsylvania

1.Look at the right side (upper or lower corner) under the map name, or the second of two numbers separated by "x", to find the width scale (longitude) of the map: If "7.5 Minute Series" enter 450 If "15 Minute Series" enter 900 If "15x30 Minute Series" enter 900 _________________ See Image Item 1	If the map does not have this you can aslo tell by the scale. 1:24000= 7.5 minute 1:62,500 = 15 minute
2.Using a ruler, measure the width of your map east to west (Exclude the borders) __________________cm See Image Item 2	Latitude and Longitude are often defined in degrees, minutes, and seconds. There are 60 seconds in a minute and 60 minutes in a degree. The symbols are as follows
3.Divide the #1 by #2 to the nearest whole number ________________cm/sec	° = degrees ' = minutes " = seconds
4.Enter the Longitude located in the lower right hand corner ______________° ' " See Image Item 4
5.Using a ruler, measure (cm) from your site, straight across to the right hand side of the map. _________________ cm See Image Item 5
6.Multiply #5 by #3 (to the nearest whole number) __________________
7.Convert #6 to minutes and seconds by dividing by 60. Your whole number after division is the number of minutes, and the remainder is the number of seconds. (Do not use a calculator) For example, 215 can be divided by 60 three times. 215-180=35. So 215 converts to 3'35". ___________________
8.Add #4 to #7 ___________________ The answer to #8 is the Longitude of your site.

STEP 3: Calculating Latitude
9.Look at the right side (upper or lower corner) under the map name, or the second of two numbers separated by "x", to find the width scale (longitude) of the map: If "7.5 Minute Series" enter 450 If "15 Minute Series" enter 900 If "15x30 Minute Series" enter 900 _________________
10.Using a ruler, measure the length of your map north to south (Exclude the borders) __________________cm See Image Item 10	For a partial printout of a map, measure one full section and multiply. For example, in the sample 1:62,500 scale map shown, only one full vertical section is shown. To get the full map size as needed, measure the top to bottom length of a full 5 minute section and multiply by 3. (3 x 5min = 15 minute or 1:62,500 scale map)
11.Divide the #9 by #10 to the nearest whole number ________________cm/sec
12.Enter the Latitude located in the lower right hand corner ______________° ' " See Image Item 4
13.Using a ruler, measure (cm) from your site, straight down to the bottom of the map. _________________ cm See Image Item 13
14.Multiply #11 by #13 (to the nearest whole number) __________________
15.Convert #14 to minutes and seconds by dividing by 60. Your whole number after division is the number of minutes, and the remainder is the number of seconds. (Do not use a calculator) For example, 215 can be divided by 60 three times. 215-180=35. So 215 converts to 3'35". ___________________
16.Add #15 to #12 ___________________ The answer for #16 is the Latitude of your site.