Shapefile Coordinate Transformation Utility
Download 1.1b Setup
Wizard / Source
Kit / Command
SHPTRANS is a fast, high-precision NTv2 datum
transformation and projection utility which reads and writes shapefiles.
SHPTRANS is intended to complement, not replace, existing
projection tools such as those within ArcView GIS 3.x and ArcGIS 8.x.
Datum Support: SHPTRANS supports three datums /
spheroids: NAD83 (GRS 1980 / WGS 1984), NAD27(Clarke 1866), and ATS77
(roughly, WGS 1972). If you want to transform between datums, a
grid-shift file is required in NTv2 format. The Canadian NTv2 grid-shift
file, used to transform between NAD27 and NAD83, is available for
purchase from Natural
Resources Canada. ESRI Canada has an agreement with NRCan, so that
ESRI customers may obtain the grid-shift file for free.
There is a grid-shift file to transform between ATS77 and NAD83 for
Atlantic Canada. This may be available from Nova Scotia Geomatics
Centre, although I couldn't find it online. A much more detailed
ATS77<->NAD83 grid-shift file covering only the province of New
Brunswick is available from Service New Brunswick as part of NBGeoCalc. An updated
grid-shift file is also available for PEI, and I understand the Nova
Scotia high-res gridshift file is in the works.
If you have both the NAD27-NAD83 grid-shift file and an appropriate
ATS77-NAD83 grid shift for your study area, SHPTRANS will
convert in either direction between all three datums. If you have neither
grid-shift file, you will not be able to convert between datums, but you
can still use SHPTRANS to reproject without changing the
Projection Support: SHPTRANS supports the
following projections: UTM (tested for North America; intended to support
all 60 zones in both hemispheres), MTM 3-degree (tested for Atlantic
Canada; intended to also support Quebec), arbitrary TM (any TM projection
with 0 as the latitude of origin); as well as the Double Stereographic
projections used in New Brunswick and Prince Edward Island. The input and
output coordinate system can be any of these projections, or lat/long
decimal degrees. If a projection is specified, the map units are taken as
metric by default. (However, with the latest development versions, you
can specify other units such as kilometres, feet, or miles.)
This program was written for Win32. It includes a command line utility
for use in batch conversions, and an ArcView 3.x extension to provide a
Version 1.1 of the ArcView 3 extension did not work on newer
versions of Windows (ME, 2000, and probably XP). Correcting this problem
was the focus of the 1.1a release. In the event that the ArcView
extension still does not work on some version of Win32, please try the
command line version of the utility. The command line tool works on all
known Win32 platforms.
Version 1.1b and later are developed and tested primarily on
Windows XP, but should continue to work on other Win32 platforms.
I'm not doing anything fancy or Windows XP - specific.
ArcGIS 8.1 Projection Engine: ArcGIS 8.1 does not require
SHPTRANS in order to perform NTv2 datum conversions. The
NTv2 capability, and the Double Stereographic projection, have been
integrated into the core ArcGIS projection engine. This means that ArcGIS
can not only reproject ahead of time like SHPTRANS does
(saving the result to a new file), but can also transform and project GIS
layers on the fly.
Future Development: So where does this leave
SHPTRANS? ArcGIS's built in capabilities go beyond
what the SHPTRANS GUI for ArcView could do, so there's
no reason to port that extension to ArcGIS. However,
SHPTRANS seems to be significantly faster than ArcGIS for
NTv2 transformations at this point in time, and the command-line interface
is very convenient for large batch jobs. Future work on the
SHPTRANS command line tool might include having it use a
.prj file if one is available, and on systems where ArcGIS is installed,
it might integrate the projection engine to support a wider range of
datums and projections. Future work might also involve supporting
additional projection libraries such as PROJ.4. Help is welcomed in any
of these areas.
Open Source: SHPTRANS is an open source, free
utility. You can view the license
here. These license terms do not apply to version 1.1a and
earlier. You may continue to use those versions under the old license,
of course, but the source code is only available for 1.1b and later.