Get and Set Lat/Long Extent of Map View in QGIS

Question

I am new to QGIS, and assume this question is a basic one and can be easily answered. However, I was not able to find the answer by trying things out, searching the web, or reading QGIS tutorials.

I want to export a png showing a section of a map from QGIS (I used Natural_Earth_quick_start_for_QGIS.qgs with WGS 84 / Pseudo Mercator) and want to know the extent in latitude and longitude values.

I tried to do that with the Print Composer. I tried to set distinct lat/long borders in Extents, but I really wasn't able to find a mapping between lat/long values and the values in the Extents edit fields.

As stated above, I was not able to find the answer in tutorials (e.g. http://www.qgistutorials.com/en/docs/making_a_map.html) and the description in the doc isn't helpful either, see https://docs.qgis.org/2.8/en/docs/user_manual/print_composer/print_composer.html#extents

I want to be able to use two approaches:

1. Define a map section by mouse, as possible in the Print Composer, and obtain the corresponding lat/long borders.
2. Set the lat/long border values manually an obtain the corresponding map section.

How can I do that?

Answer 1

The units in the print composer extents are the units used for the coordinate reference system of the map. Your project is in WGS 84 / Pseudo Mercator, which uses meters as its units. If you want to use lat/long, change the project CRS to EPSG: 4326, WGS 84 (not pseudo mercator).

You can find the coordinates of any point on your map using the Coordinate Capture tool from the Vector Toolbar.

Note: The Coordinate Capture tool allows you to select a different CRS from the project CRS. If you wanted to, you could leave the project in WGS 84 / Pseudo Mercator while using WGS 84 for this tool.