0

I am new to GIS, and am to cluster geospatial datapoints using DBScan() in the fpc package on R. However, my dataset is in ESPG 4326 (WGS 84). Since WGS 84 stores lat-long as degrees, and not metres.

I am doubtful what CRS I should project my layer onto, in order to enable using DBScan. I have spatial data points from throughout the world (except Antarctica) and would be comparing the vicinity of each spatial datapoint for the presence of other points (so that I can merge them using DBScan). Since my points are spread throughout the world, I don't think it makes sense for me to use any one site-specific CRS. (I am not sure of this, and would like to know your thoughts)

Any suggestions on what is usually done in such circumstances?

4
  • 1
    I'm wondering if you couldn't run the DBScan on the degree based data. Have you tried doing so?
    – Erik
    Commented Jul 12, 2022 at 13:12
  • Hey Erik, I did try running DBScan on the degree-data itself, and it works okay. I also cross checked it by plotting it on mapview(). However, to set the 'eps' argument for DBScan, I set the distance arbitraily. I am not sure what an "distance" means when I define it to be 0.05, and subsequently use this as the eps argument to DBScan. Commented Jul 12, 2022 at 13:51
  • You have another problem, global-wise -- the shortest distance might be across the date-line (+/-180).
    – Vince
    Commented Jul 12, 2022 at 14:29
  • Hey Vince. Specifically, I am interested in comparing very small scales. I have a bunch of entries that are repeated within +- 10m of each other. I want to combine all these entries into a single cluster. I would like to do this small-scale clustering for all points I have to see the 'hotspots' of the entries. Commented Jul 13, 2022 at 6:25

1 Answer 1

-3

You have the pseudo Mercator projection using EPSG 3857 in meter. enter image description here The accuracy is 2 meter.

Using the reprojection tool you can convert your lon / lat in ° to X / Y in meter: enter image description here

2
  • 1
    Web Mercator does not have an accuracy of 2 meters, and all measurements in Web Mercator are useless for distance or area calculation.
    – Vince
    Commented Jul 12, 2022 at 13:11
  • EPSG 3857 doesn't provide reliable distance and area-measurements.
    – Erik
    Commented Jul 12, 2022 at 13:11

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.