How to creat a new location projection file(*.prj) in arcgis?

How to creat a new location projection file(*.prj) in arcgis?

you can modify a *.prj in a text editor or edit it within the standard interface. What exactly do you want to do before further suggestions are made.

I want to transform the Beijing54 Projected Coordinate system to the local Projected Coordinate system.And I already know the four parametres of the single point'transformation.But my classmate tell me this parameters are not the parameters that what I need to define the local Projected Coordinate system?

Yes,yes,Ialready know the parameters(Translation and rotation parameters ,roportion coefficient) between this two Projected Coordinate system,.but when I use the Project tool, I don't know how to define the local Projected Coordinate system,like the second picture?

Ok, have you tried creating a custom projection as described here: 30583 - Create a custom projection file with units of feet or meters in ArcMap?

- 3 people found this helpful
I think you are muddling up 2 separate things here.

1. Creating a new (local) coordinate system definition.

2. Creating a custom datum transformation.

So for 1., if you have a similar (like your Beijing 54) existing coord sys, in the coord sys tab, just select it and right click. 3rd option is to copy and modify. Give it a new name, make your changes, then save and add to favourites.

2. Is to use the Create Custom transformation tool as Sephe suggests. Make sure you know what type (method) of transformation you are defining.

Yes, The Local Projected Coordinate system is through the translation、rotation and zoom of Beijing54 Projected Coordinate system,and now I know this parameters,but how can I set the

False_easting,False_northing,Central_meridian,Scale_factor,Latitude_origin? Is this five values have relation with the parameters of translation、rotation and zoom?

Thank you!

- 3 people found this helpful
Thanks, Sephe Fox !

Our datum transformation method are all between two geographic coordinate systems, not two projected coordinate systems, so the given transformation values don't apply to these methods (the translation/rotation/scale difference parameters are in a 3D Cartesian system, XYZ)

Similar conversions usually occur with CAD data, so in ArcMap, you can apply translation, rotation, scale parameters to a CAD dataset. If the data isn't part of a CAD dataset, the closest solutions would be:

1. Create a set of control points using the transformation parameters and use the Spatial Adjustment toolbar

2. Create a custom "Local" or "Hotine oblique Mercator" projected coordinate system in ArcMap. You can use the translation, rotation, scale values are starting values for the projection parameters.

This gets difficult because you're building an approximate fit, rather than a direct transformation. What you need are two corresponding points (control points!) in the two coordinate systems. Leave the 'local'/target one undefined. At both datasets to ArcMap. Now define the custom projected coordinate system in the data frame. You can now keep adjusting those parameters. The 'known' data will be projected on-the-fly to the new, custom coordinate system. If you can get the known data to overlay with the 'local'/unknown data, then you've figure out the unknown data's coordinate system. I'm attaching a document written by Willy Lynch, who used to work at Esri.

Melita

Thanks, Sephe Fox !

Our datum transformation method are all between two geographic coordinate systems, not two projected coordinate systems, so the given transformation values don't apply to these methods (the translation/rotation/scale difference parameters are in a 3D Cartesian system, XYZ)

Similar conversions usually occur with CAD data, so in ArcMap, you can apply translation, rotation, scale parameters to a CAD dataset. If the data isn't part of a CAD dataset, the closest solutions would be:

1. Create a set of control points using the transformation parameters and use the Spatial Adjustment toolbar

2. Create a custom "Local" or "Hotine oblique Mercator" projected coordinate system in ArcMap. You can use the translation, rotation, scale values are starting values for the projection parameters.

This gets difficult because you're building an approximate fit, rather than a direct transformation. What you need are two corresponding points (control points!) in the two coordinate systems. Leave the 'local'/target one undefined. At both datasets to ArcMap. Now define the custom projected coordinate system in the data frame. You can now keep adjusting those parameters. The 'known' data will be projected on-the-fly to the new, custom coordinate system. If you can get the known data to overlay with the 'local'/unknown data, then you've figure out the unknown data's coordinate system. I'm attaching a document written by Willy Lynch, who used to work at Esri.

Melita