3 replies to this topic

[dddino]

Hi guys,

Forgive me for being new to cartography - but I thought I'd ask experts for a pointer. I am unsure of the proper terminology even, but, I believe that what I need to do is convert coordinates from SPCS to latitude, longitude.

What I am looking for is a mathematical formula for the conversion. I need to write a program to do this but was unable to find a formula online. The only example of code that I was able to find was written in 1986, in Fortran - so - that's about as cryptic to me as (I'm sure) I sound to you in my vague description of data.

This is the information about the system as I could determine:

• 1927 North American Datum (NAD)
• Maryland State Plane 10,000 foot grid values

There is a website that has a web version of the mentioned fortran program, and it's located at ngs.noaa.gov

Example input/output:

NAD27
Northing = 458000.000
Easting = 933000.000
Zone = 1900

Output:
Lat 39 5 24.05008
Lon 76 31 53.13491

I hope that this example explains what I am looking for. Is there an online resource explaining these formulas that anyone could point me to?

Thanks for your time.

[dddino]

As a follow-up to my question, for any programmers out there:

There are two solutions I ran into. One is using a library called "Proj.4" -- a free Cartographic Projections library. It can convert from NAD27 to lat / lon. The library can be found at http://trac.osgeo.org/proj/

The second solution was using f2c (fortran to c converter) - the original 1986 code from the government site I mentioned still works today, as long as you convert it and compile it.

Hope this helps someone.

[Rob]

if you have access to a gis, this will take about five minutes.

else, post your data here and maybe someone can run it for you. i'd straight up offer but i'm on the road with spotty networks. good luck.

[dddino]

if you have access to a gis, this will take about five minutes.

else, post your data here and maybe someone can run it for you. i'd straight up offer but i'm on the road with spotty networks. good luck.

Thanks for the kind reply Rob. The problem is that coming from a software development angle, I am not familiar with GIS software - and even worse, don't have access to it. My application has literally been to reinvent the wheel (or at least just one tiny portion of it) for a permanent (and automated) data import. I just didn't know where to get the foundational information about these projections and conversions and picking brains of experts seemed like a good idea.

In the end, I ended up implementing the solution as I described in my previous message. Thanks again for your reply.