FAQ's

1) Does it matter which side of the screen is used for the Input side and which is the Output side when performing Interactive Conversions?

It does not matter which half of the screen is designated as the Source (Input) side or the Destination (Output) side in the Geographic Calculator.

 

2) When I install a second Blue Marble Application, do I need a separate geocalc.dat file?

A second geocalc.dat is not needed. Blue Marble applications allow the user to use a ‘universal’ geocalc.dat. That way, if the file is updated with user defined parameters, all applications can use the updates.

The path to geocalc.dat can be set by navigating to Options images/GEOCALCHELP00090000.gifPreferences images/GEOCALCHELP00090000.gifGeneral and changing the path in the Coordinate Conversion Parameter Database. Set this path in all Blue Marble applications to use the same geocalc.dat.

It is recommended that a backup of geocalc.dat be made before changing it in any way.

 

3) I need to use the NTv2 grid shift files for my project. How do I obtain these files?

NTv2 grid shift files are only available through the Canadian government. For more information on purchasing or licensing for development, please contact:

 

Address:

Client Services Unit

Geodetic Survey Division

Room 440

615 Booth Street

Ottawa, Ontario

K1A 0E9

Phone: (613) 995-4410

FAX: (613) 995-3215

Email: information@geod.NRCan.gc.ca

Web: http://www.geod.NRCan.gc.ca

 

6) The coordinate system that I want to use is not predefined in the Geographic Calculator. I need to find the parameters associated with my coordinate system. What reference source should I check for these parameters?

Sometimes, a user may need to look up a unit of measurement or ellipsoid parameters for a particular project. A good resource for finding such parameters is the European Petroleum Survey Group (ESPG). This database can be accessed on the Internet at the following URL:

http://www.epsg.org/

 

8) What is the difference between US State Plane 1927 and US State Plane 1927 (Exact solution)?

There are two forms of State Plane 1927: State Plane 1927 and State Plane 1927 Exact. State Plane 1927 is the first State Plane system developed for the United States. It is based on tables and coefficients for each zone in each state. The State Plane 1927 Exact is a revised version of the original State Plane 1927 system. It uses pure projection equations to calculate points for conversion.

 

9) I spend a lot of time searching for the appropriate items in the scroll down menus. Is there an easier way to find the items?

You can navigate to the correct area of the scroll down menu by typing the first letter of the item you are looking for. For example, if you are looking for NAD27, type "N" and the scroll down menu will automatically advance to the items that begin with the letter "N".