Timeline for Calculating areas of world map in QGIS?
Current License: CC BY-SA 4.0
4 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jun 27, 2019 at 16:52 | comment | added | csk | Nope. You have to use your own judgement to choose the best local CRS. Refer to radouju's comment for additional considerations. Another approach is to do the entire calculation at once in a worldwide "equal area" CRS. Compute the margin of error compared to some known areas (be sure to look at the error for features at a variety of different latitudes), and decide if that margin or error is acceptable to you. | |
| Jun 27, 2019 at 12:28 | comment | added | philsch | Thanks for all the help! One question regarding the "local_CRS" field: Is there some automated way, e.g. using Python code, to loop over local CRS? Thus, can you tell QGIS to automatically do this calculation with the respective local CRS? | |
| Jun 26, 2019 at 6:59 | comment | added | radouxju | a local CRS will provide the highest fidelity if you look at all properties of the projected polygons (distance, area, azimuth and angles), but local CRS are nevertheless specialized for a single feature (e.g. they will be conformal OR equal-area OR equidistant ). Because they are local, the distortions of the features that are not the main feature will be usually very small. However, a local conformal projection will be inaccurate for the areas (of course you will not notice it if you work in square kilometers, because the error will usually be very small). | |
| Jun 25, 2019 at 18:21 | history | answered | csk | CC BY-SA 4.0 |