the population density service has been double checked
From the database, one can find weird results for the population_density-service; the following might serve as an example.
The command
SELECT station_id,name,ST_AsText(coordinates),mean_population_density_250m_year2015
FROM stationmeta_global g, stationmeta_core s
WHERE s.id=g.station_id AND
mean_population_density_250m_year2015<0. AND
mean_population_density_250m_year2015 <> -999 AND
mean_population_density_250m_year2015<> -1; returns the following result:
station_id | name | st_astext | mean_population_density_250m_year2015
------------+----------------------------------------+----------------------------------------------------+---------------------------------------
15867 | | POINT Z (0 0 0) | -12944.968722156656
22916 | Storebaelt | POINT Z (11.035509 55.34213 250) | -22763.392690517703
16 | Montes Chaos - Sines | POINT Z (-8.833333 37.933334 103) | -16412.4923074998
13752 | Berlin Leipziger Straße | POINT Z (13.382363 52.509801 40) | -13306.271659488171
13753 | Oldenburg Heiligengeistwall | POINT Z (8.21197 53.142815 9) | -13079.0761826572
19906 | | POINT Z (-122.586111 48.491944 1) | -19532.931354535493
4566 | IE0031R | POINT Z (-9.904444 54.326667 -999) | -22197.849775637464
20386 | Deokjeokdo | POINT Z (126.3159 37.2333 -9999) | -16258.879698041686
7858 | IT2168A | POINT Z (0.00006871258524 0.000404465917681 -999) | -12944.968722479201
7525 | CY0004A | POINT Z (0.000299568186688 0.000315775285609 -999) | -12944.968722353256
11030 | Sunny Farms West | POINT Z (-83.423448 0.410931 -999) | -12945.301667437228
6257 | Lennon Drive | POINT Z (146.862 -19.2589 -999) | -13712.341568216847
6203 | LNA | POINT Z (-86.8072 30.0928 -999) | -14961.57275233884
9482 | 大海花园 | POINT Z (108.3506 21.6414 -999) | -13926.655181019067
10255 | Borivali East, Mumbai - MPCB | POINT Z (72.52048 19.13276 -999) | -13701.835299118557
10477 | Khindipada-Bhandup West, Mumbai - IITM | POINT Z (72.55339 19.09918 -999) | -13699.05230183991
13754 | Rotterdam Noord -Statenweg | POINT Z (4.4617 51.9269 0) | -12984.316943491078
3918 | VINARÒS PLATAFORMA | POINT Z (0.70917 40.38333 -999) | -16994.2399083757
16349 | | POINT Z (-67.999445 44.000085999999996 0) | -17995.650288793866
16887 | | POINT Z (-81.266751 30.611071999999997 15) | -15041.032182969311