Linked Questions

13 votes
2 answers
7k views

ArcGIS Length and Area Calculation Scenarios [closed]

Trying to get a handle on how length and area are calculated in different scenarios in ArcGIS. I don't know why I can't find a answer on the feature class fields, but I can't find a precise answer, ...
awesomo's user avatar
  • 3,421
12 votes
1 answer
12k views

Calculating area of an EPSG:4326 Polygon [duplicate]

Possible Duplicate: What is the most accurate coordinate system for calculating areas of polygons? In our Postgres/Postgis database we store polygons in a column defined as lonlat/EPSG:4326, as ...
Anders Jakobsen's user avatar
11 votes
2 answers
705 views

Why do I get correct area and intersect area when use wrong projection?

I need to calculate areas and intersection areas for polygons (some real geographical objects like lake, city, country, e.t.c.). Polygons located in California, New Zealand, Russia.Anadyr, Sweden All ...
Capacytron's user avatar
8 votes
1 answer
8k views

How to measure areas of features in OpenLayers plugin background maps correctly?

I can't figure out how to make areal calculations (eg. in km2). I have tried the 'field calculator', I have tried the 'measure area' function on the "attributes" toolbar, and i have tried fTools in ...
Lasse Jesper Pedersen's user avatar
5 votes
0 answers
369 views

Intersection and area calculations in geographic vs. projected coordinates

I think one should do intersection calculations when layers are in the same coordinate system, and one should do area calculations in the appropriate projected coordinate system. The order matters, ...
JPC's user avatar
  • 71
4 votes
3 answers
1k views

Which equal-area projection to use for UK?

I have a bunch of UK polygons that are saved in my PostGIS database as WGS84 projection. I would like to calculate the area of these polygons using st_area. According to this answer I can save these ...
Richard's user avatar
  • 3,251
4 votes
2 answers
3k views

Polygon area calculation in Ruby (on Rails, rgeo, PostGIS and GEOS) in sqare meters

In a Ruby-on-Rails application, I need the area in square meters (or any other surface measure, be it ares, hectares, square kilometers, but not in pseudo surface measure like square degrees) of a ...
das-g's user avatar
  • 1,445
4 votes
2 answers
20k views

What are the units of the calculated area from a raster in decimal degree

I'm trying to calculate area for a raster file which contains 2 layers (0 for unsuitable habitat and 1 for suitable). It's been calculated successfully but I don't know what is the unit of the ...
Mah's user avatar
  • 305
4 votes
1 answer
193 views

Why does not equal length of line in DIRECTION/LENGTH with length of line in MEASURING in OpenLayers 2.13? [duplicate]

My map projection is: "EPSG:900913", display projection is "EPSG:4326" and units is "m", however does not equal the length in Direction/length with the length is calculated in measuring in OpenLayers, ...
Samane's user avatar
  • 989
3 votes
1 answer
945 views

PostGIS: calculate area of intersection of EPSG:27700 polygons?

I have two tables in Postgres, both of type geometry(MultiPolygon,27700) and I would like to find any that intersect with an area of more than 100 square metres. I know how to get any that intersect ...
Richard's user avatar
  • 3,251
3 votes
2 answers
695 views

How to calculate area in sq m - troubleshooting projection issues in a global dataset in QGIS

I am using QGIS version 2.12.3. I have 3 polygon shapefiles: A, B and the intersect of A and B, which we can call C. All I want is to add a field to the attributes table of each shapefile giving ...
ElephantTwelve's user avatar
3 votes
0 answers
68 views

Projecting polygon when calculating its area using R? [duplicate]

I have a broad range of polygons (in vector format and in SpatialPolygonsDataFrame class), some going east-west, others going south-north, while even others span polar regions or very large ranges as ...
jO.'s user avatar
  • 361
2 votes
1 answer
729 views

Changing projection for field calculator

I've just succeeded in getting the area of a polygon using field calculator. The polygon was drawn on a Google hybrid aerial photo. There are no units given in the calculation and I assume the area ...
otis_b_flywheel's user avatar
2 votes
1 answer
375 views

Area of an EPSG 27700 polygon

I am working with EPSG 27700 polygon data in PHP. All the polygons are in the UK. The polygons do not have holes inside them. I'm hoping to be able to calculate the area of these polygons. For this I ...
Christopher Gutteridge's user avatar
2 votes
2 answers
1k views

How does the projection of a dataset affect the results of spatial analysis?

I am planning on conducting a multi-criteria-analysis with a number of different source datasets. A number of the datasets are found in different coordinate systems and projections. Do I need to ...
rgmrtn's user avatar
  • 215

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