Re: How to convert coordinates

Corpscon is plenty accurate enough.  However there are two components to
Corpscon that often get confused.  First of all latitude and longitude may be
referenced to different datums.  The principal datums commonly used are
termed NAD27 and NAD83.  GPS gives a value in the WGS84 datum which is very
very close to NAD83.  Given one of those particular datums corpscon can
convert it to the corresponding State Plane coordinates very accurately.
However if you are going from a lat/long in NAD27 to a State Plane in NAD83
there is no exact converstion.  Corpscon uses the most exact method known
which is the so called NADCON conversion.  It is a model of the differences
between NAD27 and NAD83 based on a subset of the stations common to both
systems. It is probably going to give you a conversion to better than a foot
accuracy if you are going 'cross datums'.

To summarize Corpscon will give correct and nearly exact conversions within
either NAD27 or NAD83 datums of lat-long to SPC.  It cannot do a precise
conversion across datums, but it does as good as can be done without local
survey network analysis and is more than good enough for many applications.

Please feel free to reply or email me directly if you have any further
questions.

- Jerry Wahl

PS the NGS web site at www.ngs.noaa.gov has links to online computations of
lat long to SPC but you will find that the same issues apply.



PEL wrote:

> Hello,
>
> I am looking for an accurate (survey level precision of 5 decimal places)
> Coordinate converter program that can convert from Lat-Long (either in
> decimal or deg-min-sec) to State Plane Coordinates (California), and then
> vice-versa.  I know of Corpscon, but I've heard that it is not accurate
> enough for my application.
>
> Thanks in advance for your replies.
>
> Phil in Orange County, CA