Parent Topic: DATUMS
GRID SHIFT FILES
In V6.2 (and earlier versions back to V6.0.1), the negative datum codes were hard-coded to link them with certain grid-file formats: 

 Datum   Datum Name                                       Ellipsoid
 Code      Location                                       used

 "D-01"  NAD27 (USA, NADCON)                              "E000"
           Continental U.S.                                Clarke 1866
             Uses NADCON files ("conus.los", "conus.las")

 "D-02"  NAD83 (USA, NADCON)                              "E008"
           Continental U.S.                                GRS 1980
             Uses NADCON files ("conus.los", "conus.las")

 "D-03"  NAD27 (Canada, NTv1)                             "E000"
           Canada                                          Clarke 1866
             Uses NTv1 file ("grid.dac")

 "D-04"  NAD83 (Canada, NTv1)                             "E008"
           Canada                                          GRS 1980
             Uses NTv1 file ("grid.dac")
For V6.3, this assumption has been relaxed. There is no assumed coupling of the negative datum code and the format of the grid file(s). The software will read the grid-file, decide what format it is and if it is a supported format will use it.

For V6.3, there are three grid-shift formats supported:


NADCON files
There are three sets of the U.S. NADCON (North American Datum Conversion) grid-shift files provided in the $PCIHOME/etc directory: 

 Datum   Datum Name                                       Ellipsoid
 Code      Location                                       used
             (File in $PCIHOME/etc)
               Area covered

 "D-01"  NAD27 (USA, NADCON)                              "E000"
           Continental U.S.                                Clarke 1866
             ("conus.los", "conus.las")
               Longitudes:  63d W to 131d W;
               Latitudes:   20d N to  50d N;
               Resolution:  15 minutes

 "D-02"  NAD83 (USA, NADCON)                              "E008"
           Continental U.S.                                GRS 1980
             ("conus.los", "conus.las")
               Longitudes:  63d W to 131d W;
               Latitudes:   20d N to  50d N
               Resolution:  15 minutes

 "D-05"  NAD27 (USA, NADCON)                              "E000"
           Alaska                                          Clarke 1866
             ("alaska.los", "alaska.las")
               Longitudes: 128d W to 169d W;
               Latitudes:   50d N to  74d N

 "D-06"  NAD83 (USA, NADCON)                              "E008"
           Alaska                                          GRS 1980
             ("alaska.los", "alaska.las")
               Longitudes: 128d W to 169d W;
               Latitudes:   50d N to  74d N

 "D-07"  Old Hawaiian (USA, NADCON)                       "E000"
           Hawaii                                          Clarke 1866
             ("hawaii.los", "hawaii.las")
               Longitudes: 154d W to 161d W;
               Latitudes:   18d N to  23d N

 "D-08"  NAD83 (USA, NADCON)                              "E008"
           Hawaii                                          GRS 1980
             ("hawaii.los", "hawaii.las")
               Longitudes: 154d W to 161d W;
               Latitudes:   18d N to  23d N
Other NADCON files (e.g. for Puerto Rico and the Vigin Islands; the Alaskan islands of St. George, St. Lawrence, and St.Paul) are available on the Internet at ftp://ftp.ngs.noaa.gov/pub/pcsoft/nadcon or by FTP at ftp.ngs.noaa.gov in the pub/pcsoft/nadcon subdirectory.


NTv1 files
There is one Canadian NTv1 (National Transformation, Version 1) grid-shift file provided in the $PCIHOME/etc directory: 

 Datum   Datum Name                                       Ellipsoid
 Code      Location                                       used
             (File in $PCIHOME/etc)
               Area covered

 "D-03"  NAD27 (Canada, NTv1)                             "E000"
           Canada                                          Clarke 1866
             ("grid.dac")
               Longitudes:  44d W to 142d W;
               Latitudes:   40d N to  84d N
               Resolution:  15 minutes

 "D-04"  NAD83 (Canada, NTv1)                             "E008"
           Canada                                          GRS 1980
             ("grid.dac")
               Longitudes:  44d W to 142d W;
               Latitudes:   40d N to  84d N
               Resolution:  15 minutes

NTv2 files
Although support has been added for EASI/PACE V6.3 for the Canadian NTv2 (National Transformation, Version 2), no NTv2 grid-shift files are provided in the $PCIHOME/etc directory as the grid-shift files are proprietary.

Information on obtaining the NTv2 data ($195 Canadian per CDROM) should be directed to: 

 Geodetic Survey Division,
 615 Booth Street,
 Ottawa, Ontario,
 Canada  K1A 0E9

 Attn: Client Services

 Tel:  (613) 995-4410
 Fax:  (613) 995-3215
If you have the NTv2 CDROM and want the PCI software to use it, you would do the following:

1.) Activate the datum code records. In the datum.txt file in the PCI home etc sub-directory (e.g. $PCIHOME/etc/datum.txt), there are four records defined for NTv2. These records are commented out at present and can be activated by removing the exclamation mark at the front of the records.

For example, change... 

!"D-86","NAD27 (Canada, NTv2)","E000","Canada","ntv2_0.gsb"
!"D-87","NAD83 (Canada, NTv2)","E008","Canada","ntv2_0.gsb"
!"D-88","MAY76 (Canada, NTv2)","E000","Canada","may76v20.gsb"
!"D-89","NAD83 (Canada, NTv2)","E008","Canada","may76v20.gsb"
To... 

"D-86","NAD27 (Canada, NTv2)","E000","Canada","ntv2_0.gsb"
"D-87","NAD83 (Canada, NTv2)","E008","Canada","ntv2_0.gsb"
"D-88","MAY76 (Canada, NTv2)","E000","Canada","may76v20.gsb"
"D-89","NAD83 (Canada, NTv2)","E008","Canada","may76v20.gsb"
2.) Decide where you want the NTv2 files to reside and update the file name accordingly in the four records listed above.

A simple file name (e.g. "ntv2_0.gsb") would be searched for first in the local work account. If no file was found by that name, a search is made for it in $PCIHOME/etc.

Variations of simple file names are acceptable. For example, you could put a pathname in the filename in the datum.txt records noted above. (e.g. "/usr/etc/ntv2_0.gsb" or "c:\usr\etc\ntv2_0.gsb").

Please note that although support has been added for NTv2, PCI is still in the process of obtaining accreditation from the Geodetic Survey Division in supporting the NTv2 file format.

Parent Topic: DATUMS
About PCI Help Gateway