Freelance Historian
The World of Historical Manuscripts and Ephemera

DH

Posted in   by Steven on August 12th, 2017

Details on how I determined that the site we had marked “DH 1&2” was really DH 5, and how I plotted where the “real” DH 1&2 is.

Here are all the GPS coordinates you have given me, plotted from the Google Map to the topo map, plus the calculated location of DH6:

If we lay the 1883 map over this, we can see that the location we have marked DH1&2 is way too far to the left to be correct. Since according to the 1883 map, DH5 has to be just to the right of that creek branch, there is no way to stretch the map to make those GPS coordinates work as DH1&2. It would put DH5 way to the left of the creek branch.

This is a close-up with the creek branch marked in blue. It has gone dry in the present day, but the valley it was in is still there:

 

 

 

This image shows the 1883 map over the Google GPS map. If DH3 and DH6 are in the right spot, the location we have marked DH1&2 is way too far to the left.

How I Found The Real DH 1&2

(Warning: heavy math ahead)

so, with the map telling us that the site to the left is really DH5, the question becomes “where is DH 1&2?” First, I overlay the 1883 map on top of the GPS coordinates, and match the terrain:

 

I made a 1000-ft long ruler to match the Google Maps at this scale:

 

Then, I measured the distance in feet between the three known points and the bottom of the J. We are going to use these measurements to calculate the latitude and longitude of the real DH1&2 from three separate directions, to be sure we have it correct. First, I had to draw lines at 90 degrees between the bottom of the J and our three known points. :

 

 

Then we measure the distance west or east, then north or south from our three locations to the bottom of the J. It is about 510 ft west and 225 ft north of DH6:

 

 

It is about 275ft west and 80ft south of DH3:

 

 

and about 410ft east of the old DH1&2. (it’s hardly north at all)

 

MATH

TO calculate the GPS coordinates of the real DH1&2, we have to know how many feet are in one second of latitude and one second of longitude at 34°N and 84°W. I was able to find the length in feet for one degree at this latitude and divide to get seconds:

ONE SECOND OF LATITUDE AT 34°N = 101.17311 feet.
ONE SECOND OF LONGITUDE AT 34°N = 78.9463 feet.

DH3 to Target:

Target is 0.7907239 seconds south of DH3

Latitude of DH3 is 39°05’03.3″N
subtract 0.79 from 3,3, and round up to get 2.5

Target latitude is 39°05’02.5″N

====

Target is 2.2166966 seconds west of DH3

Longitude of DH3 is 84°49’32.3″W
add 2.2 to 32.3 to get 34.5

Target longitude is 84°49’34.5″W

 

DH6 To Target

Target is 2.223911 seconds north of DH6

Latitude of DH6 is 39°05’00.2″N
add 2.2 to 0.2 to get 2.4

Target latitude is 39°05’02.4″N

======

Target is 6.4600 seconds west of DH6

Longitude of DH6 is 84°49’27.9″W
add 6.46 to 27.9 to get 34.3

Target longitude is 84°49’34.2″W

DH1&2 (DH5) To Target

Target is 5.1934 seconds east of DH5

Longitude of DH5 is 84°49’39.5″W
subtract 5.2 from 39.5 to get 34.3

Target longitude is 84°49’34.3″W

 

CONCLUSION

The true location of DH 1&2 is

39°05’02.5″N,  84°49’34.3″W

(39.084028, -84.826194 decimal)

=====

Mapping Locations on Topo Map

The topo map has latitude/longitude lines crossing at

39°05’00.0″N 84°49’00.0″W,
39°05’06.0″N 84°50’00.0″W,
39°06’00.0″N 84°49’00.0″W and
39°05’06.0″N 84°50’00.0″W.

By marking these coordinates on the Google GPS map, I can perfectly transfer the locations to the topo map. I just lay the Google map over the topo map, and erase everything except the coordinates.