Linked Questions

1
vote
0answers
55 views

How to quantify projection distortion using ArcGIS [duplicate]

I am trying to figure out a workflow to quantify the amount of distortion for different projections throughout a given area of interest. I am thinking in the form that you would do a relative ...
62
votes
7answers
8k views

What strategies, criteria, or rules to use for selecting coordinate systems?

What strategies, criteria, or rules do you use for selecting coordinate systems for (a) storing, (b) analyzing, and (c) displaying GIS data? (I humbly offer my reply to a related question about ...
29
votes
2answers
9k views

Calculating areal distortion outside UTM zone?

One of my colleagues is working with data that is spread across two UTM zone. The majority of the data is in one zone, with a few outliers in another zone. He would like to know what the area ...
27
votes
4answers
11k views

Calculating distortion on Equirectangular Projection

I am trying to calculate distortion so I can distort overlaying text and forms to precisely match an image of an equirectangular projection. How does one calculate the distortion at a given latitude ...
8
votes
5answers
31k views

Calculating grid convergence (True North to Grid North)

I would like to know how to calculate the grid convergence angle between True North and Grid North for UTM maps. I am using ArcGIS 10.0 (ArcView licence). and have used the Calculate Grid Convergence ...
15
votes
2answers
3k views

Which world map projection allows comparing countries by shape and size?

The Mercator projection increases scale along with the latitude. Greenland seems larger than Australia, when in fact it is much smaller. The equal-area projections however stretch shapes away from the ...
14
votes
2answers
4k views

Projections appropriate for global analysis that preserve area and that preserve distance (but not necessarily in the same projection)

I am looking for a projection (or a set of projections) that decently preserve distances so that I can buffer every country in the world and have a similar level of minimal distortion for each. I ...
10
votes
2answers
2k views

How to determine projection parameters when customizing a projection

I am trying to customize an Albers and a Hotine Oblique Mercator (HOM) projection to minimuze distortion in the region I am analyzing. The region extends from about 51 to 62 degrees latitude, covering ...
8
votes
3answers
790 views

Global grid, which reference system to use?

I have seen a couple global studies using WGS84 as geographic reference, with the problem that the area of raster cells is not constant. Which reference system would you use for a global analysis in ...
9
votes
1answer
2k views

An example Tissot ellipse for an Equirectangular Projection?

I am trying to calculate distortion of an equirectangular projection via Tissot indicatrices. I have tried following the directions on this post (among other things) but it is beyond my understanding ...
3
votes
1answer
2k views

Choosing Projection for Gulf coast region of USA?

What are the most appropriate datum and projection I could use for the Gulf coast region - spanning Louisiana, Mississippi, Alabama, and Florida? I have to analyze block group data along the coast.
12
votes
1answer
1k views

How big does a circular geofence need to be for the curvature of the earth to matter? [duplicate]

I'm working on adding geofences to a mobile application. I know the proper way of calculating distance between two points on a sphere is using the great-circle or Haversine formula. I don't know if ...
3
votes
1answer
2k views

How a draw a circle (on the surface of earth) on a mercator projection?

I would like to use R and leaflet to draw a circle (a real circle on the surface of the earth) on a mercator projection. In the following code, I have the center of the circle (with lng=0 and lat=60),...
2
votes
3answers
677 views

Getting meters instead of degrees from GRASS v.distance?

I'm trying to measure the distance between points to a coastline. I have a shapefile of the "High Seas" which I got from NOAA's website here. http://www.nws.noaa.gov/geodata/catalog/wsom/html/...
5
votes
1answer
739 views

Angular distance between Grid and True North given Lat/Long

As part of a project that uses UTM coordinates I am trying to find a formula to compute the angle (with sign) between the grid north and the true north. I understand this is called meridian ...

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