Linked Questions

2
votes
0answers
25 views

What criteria should be used to select a project CRS in QGIS? [duplicate]

I've been using QGIS for a little while now, but I am still a bit confused about coordinate systems. There is plenty of guidance about how to change project and layer CRS, on-the-fly transformation ...
94
votes
16answers
50k views

Identifying Coordinate System of Shapefile when Unknown?

I have a Shapefile but its coordinate system is Unknown, and there is no *.prj file. How can I identify it now?
27
votes
6answers
11k views

Dealing with data that spreads across UTM Zones?

I have data that spreads across two UTM Zones GDA/MGA94 UTM Zone 55 and 56. I have layers such as a cadastre, roads, pipelines etc where I want to store measurements like lengths and areas in metres ...
25
votes
7answers
3k views

Spatial reference for dummies?

Can anyone recommend a good reference or tutorial that explains the principles of spatial references, projections, and coordinate systems? We are a small team of programmers working with GIS ...
24
votes
3answers
5k views

What projections should I use to make my own Globe?

Searching for an answer to this question, I found instructions posted by Gulf of Maine Research Institute showing how to create a globe. Using manual methods ... What approach would I take to ...
30
votes
1answer
6k views

How to create an accurate Tissot Indicatrix?

A Tissot Indicatrix is useful method for communicating at a glance the kinds of distortion a given projection is prone to (in the figure below, each of the red circles occupies the same area). I've ...
28
votes
1answer
6k views

Calculating Flow Direction and Delineating Basins from Projected vs. Unprojected DEM Data

This is somewhat of a theoretical question stemming from some discussions with colleagues on the topic of implications with delineating basins with projected (e.g., Albers Equal Area) vs. unprojected (...
15
votes
2answers
2k 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 ...
8
votes
3answers
757 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 ...
11
votes
2answers
3k 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 ...
9
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 ...
4
votes
3answers
760 views

Defining the appropriate Projected Coordinate System

I am a beginner at ArcGIS and have a technical question. I need to assign a projected coordinate system to my boundary/polygon data in order to calculate square miles. There are many to choose from. ...
5
votes
3answers
666 views

How to know if shapefile is georeferenced?

I have a shapefile which is located in province in indonesia. it contains many sub-province if i removed sub regions inside a shapefile, and it leaves a small region, and my question is that small ...
4
votes
1answer
2k views

Create a Rectangle around a point in PostGIS

I have just started working in PostGIS. I have a table in PostgreSQL that stores Latitude,Longitude. I want to create a rectangle of 500*500 foot around every point. Therefore, used the below given ...
3
votes
2answers
2k views

which map projection should be used for global map with geography and human demographics

I am working on a project to try to identify the most threatened populations (on a global scale) of having a limited access to freshwater. I want to compare those most at risk currently and then add ...

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