Hi There,
Our GIS department has just recently made the switch from ArcGIS 10.0 to 10.1 and we have noticed some differences in the transformations that are being suggested for our area.
Originally, using ArcGIS 10.0 when creating/manipulating maps in Atlantic Canada that required transformations between GCS_North_America_1983 and GCS_WGS_1984, we have always used NAD_1983_To_WGS_1984_1 which is a general transformation that covers all of North America. we have recently upgraded to 10.1 and after referring to the supported geographic transformation PDF (http://resources.arcgis.com/en/help/...formations.pdf) we see that NAD_1983_To_WGS_1984_1 is listed as applicable only for the USA. Is this NAD_1983_To_WGS_1984_1 transformation file the same between the two software versions and it is just defined as having a more limited use because there are other transformations available? Or rather, is this just a new file with the same name?
*after looking a little closer there are differences in their parameters.*
Page 48 of Supported geographic Transformations for 10:
Geographic (Datum) Transformation Areas of Use
Page 29 of 83 Geographic transformations for 10.1:
The recommended transformation for my area is “NAD_1927_to_WGS_1984_33 + NAD_1927_To_NAD_1983_NTV2_Canada” but will this transformation shift my data from what the NAD_1983_To_WGS_1984_1 transformation would give me and therefore create differences in the analysis completed between ArcGIS 10 and 10.1?
And one afterthought question - why the extra step in the transformation?
Thanks in advance for any clarity! my apologies if my questions seem convoluted!
Our GIS department has just recently made the switch from ArcGIS 10.0 to 10.1 and we have noticed some differences in the transformations that are being suggested for our area.
Originally, using ArcGIS 10.0 when creating/manipulating maps in Atlantic Canada that required transformations between GCS_North_America_1983 and GCS_WGS_1984, we have always used NAD_1983_To_WGS_1984_1 which is a general transformation that covers all of North America. we have recently upgraded to 10.1 and after referring to the supported geographic transformation PDF (http://resources.arcgis.com/en/help/...formations.pdf) we see that NAD_1983_To_WGS_1984_1 is listed as applicable only for the USA. Is this NAD_1983_To_WGS_1984_1 transformation file the same between the two software versions and it is just defined as having a more limited use because there are other transformations available? Or rather, is this just a new file with the same name?
*after looking a little closer there are differences in their parameters.*
Page 48 of Supported geographic Transformations for 10:
Geographic (Datum) Transformation Areas of Use
| Transformation Name | Code | Acc(m) | W-Lon | S-Lat | E-Lon | N-Lat |
| NAD_1983_To_WGS_1984_1 (North America - all Canada and USA subunits) |
1188 | 4.00 | ( 170.00, | 23.94) | (-44.00, | 80.00) |
Page 29 of 83 Geographic transformations for 10.1:
| Name | WKID | Accuracy | Area of Use | Min Lat | Min. Long | Max. Lat | Max. Long |
| NAD_1983_To_WGS_1984_1 | 1188 | 4.000 | USA (all states) | 15.5600 | 167.6500 | 74.7100 | -65.7000 |
The recommended transformation for my area is “NAD_1927_to_WGS_1984_33 + NAD_1927_To_NAD_1983_NTV2_Canada” but will this transformation shift my data from what the NAD_1983_To_WGS_1984_1 transformation would give me and therefore create differences in the analysis completed between ArcGIS 10 and 10.1?
And one afterthought question - why the extra step in the transformation?
Thanks in advance for any clarity! my apologies if my questions seem convoluted!