Converting from Clarke_1866 to WGS_1984

[DitlevReventlow]

Hey everyone.

I have to use the MCD12C1 products in an analysis. The problem is that this map is in GCS_Clarke_1866. I need it in GCS_WGS_1984. As far as I can see there is no conversion between Clarke_1866 and WGS_1984 when i try to use "Project Raster".

Therefore I when on the internet and found the following forum.

http://forums.esri.com/Thread.asp?c=93&f=984&t=152042

From here i get the impression that there is indeed no conversion between these two coordinate systems. However I also get the idea that a lot of Clarke_1866 data is really NAD_1927 or NAD_1983. Does this mean that I should just use define projection to convert to both of these? And then try to project each to WGS 1984 and see which fits best (fits best to a map that I know is WGS1984)?

How would you deal with this problem? 

Thank you very much!

Best regards

Ditlev Reventlow

[DanPatterson_Retired]

I would check with the source.. MODIS Land Team  but I do find any direct confirmation in there difficult to follow but there are some tools MODIS Land Team  assuming that reference MCD12C1 leads to the same locations.  MODIS Reprojection Tool | LP DAAC :: NASA Land Data Products and Services has projection tool set and the manual link provides more details

[DitlevReventlow]

Okay, thanks, I have tried to send the team an email. In case they can't answer then I guess the only possibility will be to try to define as both NAD 83 and NAD 27 and see which fits best after having been converted to WGS_1984, right?

[DanPatterson_Retired]

I do find it strange that they reference that Clarke ellipsoid for data that given it is North American centric but if so, there are other links that you can follow, for example this one from Spatial Reference org for the MODIS sinusoidal projection... where they cleverly tell you to google it for more information

[SachinKanaujia]

NAD27 Ellipsoid is Clarke 1866, whereas NAD 83 ellipsoid is GRS 80 which is similar to WGS84

North American Datum - Wikipedia, the free encyclopedia

You will have to use a Datum shift from NAD27 to WGS84/NAD83 whereas the shift between NAD83 and WGS84 is almost negligible

[DanPatterson_Retired]

Although Clarke 1866 does provide the basis and is largely used in the US, it is not exclusively used there

Spatial Reference List -- Spatial Reference It just happens to be best suited to North America but describes a global shape of Earth

[DitlevReventlow]

Thanks to both of you. I define it as NAD27 and transformed it to WGS 1984. Then I compared it with another map in WGS 1984 and it looks good. 

[TammieWindsor]

I'm having the same issue. I want to convert Clarke 1866 to NAD1983. I'm building suitability models and need to extract km^2, so I need the map to be fairly accurate. I'm an amateur at ArcGIS. I've tried the Project raster tool, though no Geographic transformations are available, even for other projections. I've been stuck on this for several months now.