topic Re: How to create a custom datum for ArcPad 8 in ArcPad Questions

How to create a custom datum for ArcPad 8

TobiasHeller — Wed, 14 Jul 2010 07:08:45 GMT

I have created a custom coordinate system for ArcGIS.
Now I want to specify transformation parameters using the Datum Configuration Tool.
But my custom datum doesn't appear in the list.

I can't find the place, where the datums are stored. I've read in the knowledge base, that it was stored in the past in the apDatums.dbf file. But I can't find this file in ArcPad 8.

Does anybody know, where the datums are stored in ArcPad 8?

Kind regards,
Tobias

Re: How to create a custom datum for ArcPad 8

RolfBroch — Wed, 14 Jul 2010 10:51:37 GMT

In the system folder. The files are called defaulttransforms.dbf and transforms.dbf

Rolf

Re: How to create a custom datum for ArcPad 8

TobiasHeller — Thu, 15 Jul 2010 06:14:50 GMT

Hi Rolf,

I think this is not correct.
The transforms.dbf just contains the transformation details between two datums.
The defaulttransforms.dbf contains the definition of the transformation to be used between two datums, if more than one transformation has been defined.

I've looked again into both files using Excel and a dbf editor and couldn't find details about the datum itself, just the datum name.

I know, that the datum gets stored in the prj file of a coordinate system.
But I don't know, how to get a new datum shown in the datum configuration tool.
There must be somewhere a list of datums.

Tobias

Re: How to create a custom datum for ArcPad 8

RolfBroch — Thu, 15 Jul 2010 07:05:10 GMT

I will admit that the help for datum transformation is a little lacking but using the Datum Transform Tool you add records to the two above files and enables you to download to a mobile device. For more information search ArcPad help for Define Datum and look for Introduction.

Rolf

Re: How to create a custom datum for ArcPad 8

TobiasHeller — Thu, 15 Jul 2010 09:47:20 GMT

Hi,

This is still not the answer I'm searching for.
To clarify the question:
I know how to add custom transformations to the transforms.dbf file and how to set a transformation as default in the defaulttransforms.dbf file.
This is clearly described in the Datum Configuration Tool section of the ArcPad help.

What I need to do is to add a custom datum (not transformation).
A datum consists of Spheroid name, semimajor axis and semiminor axis or inverse flattening. In ArcGIS and ArcPad, they are called D_xxxx, e.g. D_Clarke_1880.

I have created the datum already in a custom coordinate system stored in a prj file.

Now I need to specify transformation parameters from WGS84 to my custom datum. I would like to do this in the Datum Configuration Tool.
But I can't select my custom datum in the 'From Datum' combo box in the Datum Configuration tool.

My question is: How can I get a custom datum to the 'From Datum' list in the Datum Configuration tool.

Does anybody know this? Is this possible?

Regards,
Tobias