Appropriate map projection for area calculations - large features in Northern Canada

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07-03-2013 07:06 AM
MonikaTemplin
New Contributor
I would like to check that I am using the most appropriate map projection for some area calculations.
I need to run some area calculations for large features in Northern Canada. The smallest is approx 21,000 sq. km, the largest approx. 38,000 sq. km. They lie between 65°00'0"N and 83°15'00"N and approx 64°W and 93°W.

I've been doing some research and propose using the "North_Pole_Lambert_Azimuthal_Equal_Area" projection provided in ArcMap. With Central Meridian and Latitude of Origin modified to run through the approximate middle of each feature in question. Although it looks like if I keep the Latitude of Origin at 90.00000 as per the default, the area numbers do not change.

Data is in geographic, in shapefiles. Data Frame coordinate system to be set to map projection to be used (LAEA projection). Using XTools pro to populate the table specifying output projection to be same as data frame (i.e. the LAEA projection) and units=kilometres

Any Comments? Thank you for your time.
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WilliamMortimer
New Contributor III
I would like to check that I am using the most appropriate map projection for some area calculations.
I need to run some area calculations for large features in Northern Canada. The smallest is approx 21,000 sq. km, the largest approx. 38,000 sq. km. They lie between 65°00'0"N and 83°15'00"N and approx 64°W and 93°W.

I've been doing some research and propose using the "North_Pole_Lambert_Azimuthal_Equal_Area" projection provided in ArcMap. With Central Meridian and Latitude of Origin modified to run through the approximate middle of each feature in question. Although it looks like if I keep the Latitude of Origin at 90.00000 as per the default, the area numbers do not change.

Data is in geographic, in shapefiles. Data Frame coordinate system to be set to map projection to be used (LAEA projection). Using XTools pro to populate the table specifying output projection to be same as data frame (i.e. the LAEA projection) and units=kilometres

Any Comments? Thank you for your time.


Hi Monika,
It looks like you are on the correct path, however I would modify both reference lines so they fall in the centre of your target area in order to minimize distortion and scale effects. That way you can have some correct measurements from the central point - if needed.  With your area calculations its important to find out how detailed you need to go. If you only need it rounded to the nearest square km say, then you don't have to be super fussy about your projection methods. If you need to be super accurate, then you'll need to look at the local datum for that area, and splitting your data into smaller pieces and running the your calcs on those. Remember if you do modify your projection inputs.. remember to list them in your metadata somewhere as well.

You may want to look at albers equal area conic. Modify the standard parallels for your target area.
Have a look at this:
http://www.ilmb.gov.bc.ca/risc/pubs/other/mappro/map.htm
It lists the BC (British Columbia) version of albers and the uses etc.

Hope this helps.

William.
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