Topographic Maps (the making of)

[joebartels]

Having just looked at 700+ AZ topo names, dates etc. I became more curious about the making of them.

I realize I can probably find this on the net but thought we all might get some good first hand knowledge from say the zuma's, nighthiker, boynhisdog and others

Most are 1950's or 1960's
some are even mid 1940's

It just amazes me that something so accurate could be done back then.
Was the camera so huge it weighted down the plane?

Theres a couple updated ones even within the past couple years. But seems like they could be super duper in this day in time.

Was the funding security/war related?

Did somebody grid walk the entire US to find all those springs etc?

Just curious, thought it might be interesting for everybody

[Fritzski]

Good question joe. Just exactly what was the technology employed to make all those old topos? Their accuracy is impressive to say the least, especially for those pre-satellite times. I'm certain they didn't walk every square foot. It must have been a gargantuan task when you look at the entire country. Just doing the Supes would seem overwhelming to me. Who did they go to to name every one of those nondescript little canyons or springs way off the beaten path out there?

BTW I've seen where I think NASA is compiling a data base of the entire planet topographically depicted from satellite imagery. Now there will be truie accuracy!

[BoyNhisDog]

The cameras that I have seen from the '50s and '60s are actually lighter weight than the modern ones. I'm sure that I've not seen everything though. Their lenses did not have the resolution that we have now but they were not bad. The shutter speeds were slow but these folks were determined.

Once I had to fly off a map made in something like 1918. It was not as accurate at all like the ones from the '50s and '60s. Our parents and their generation were very clever. If you notice most of USGS Quads use NAD 27 (North American Datum 1927).

The natural features were identified by ground surveyors who explored and got info from the locals. Some of the original names those lonely men gave the features cannot be used on modern maps. I have seen them dissapear in my time. They were not overly PC back in those times. That is a little oversimplified but it is pretty much how they did it. 25 to 30 years ago there were many areas that were not covered by the 7.5 minute quads, just 15 minute quads. Those were hard to fly detailed areas off of. The 7.5s are wonderful. In Mexico you can't find anything more detailed than 1:50,000. A 7.5 is 1:24000.

This has been a staggering project that is always in progress. Phoenix should get an update every couple of months.

[Nighthiker]

The United States Geological Survey was est. by congress in 1879 and around 1882 a general plan was developed for the production of a standard series of topographical maps. The developed several scales 1:24,000, 1:62,500 and 1:250,000. The 1:24,000 is also refered to a quad. This map covers 7 1/2/ min. of Latitude and 7 1/2 min. of Longitude. The 1:62,500 is often called a 15 min. map, it covers 15 mins of
Latitude and Longitude. Four of the 1:24,000 maps make up a 15 min. map. The 1:250,000 map covers 1 degree of Latitude and 2 degrees of Longitude. Maps made were based on the needs at the time mapping road and train routes, navagable waterways, mining district etc. Once an area was selected for mapping and utilizing lats and longs as base lines an area would be surveyed and establishing vertical and horizontal control stations. Out hiking you may note these control stations that consists of a 3 1/2 inch brass cap. These control stations make a high degree of map accuracy 90% both horizontal and vertical. As for naming the features, they asked the locals. A friends late father named many of the place names on the Gisela and Tonto Basin quad after his wife and himself, Mary and Lou Springs and Felton Mtn. As technolgy improved surveying from the air was also utilized in making the maps.

[arizonaheat]

http://mac.usgs.gov/mac/isb/pubs/bookle ... /topo.html

This site will really give those who are interested the low down and history of topographical mapping.
Very interesting topic. Glad you brought it up Teva.

Arizonaheat

[HAZ EDIT]
As of 04/20/2005
http://erg.usgs.gov/isb/pubs/booklets/topo/topo.html

[church]

Great Site ArizonaHeat.....why not go to the source I'll recommend it as a source for book reports, essays and the like for the students/teachers at school. Uncle Sam sure has kept my rear from being lost on more then one occasion.