MVT style drops data when two points have same coordinates

[rob.j.nickerson@…]

I have set up a postcode layer and am using this in JOSM via the MVT option. A user has pointed out that when two postcodes have the exact same location, JOSM is only rendering one of them. This could lead to improper mapping. Expected behaviour: show both as is the case in the PNG tile layer I am also providing.

Example location:

51.494328 -0.212871; W14 0QR; W14 0QL; Llewellyn Mansions, Hammersmith Road and 125 Hammersmith Road.

MVT layer:
​https://api.mapbox.com/v4/robjn.3uur23nz/{zoom}/{x}/{y}.mvt?access_token=pk.eyJ1Ijoicm9iam4iLCJhIjoid0dYNkY1QSJ9.A-0lzQOawGYICYPfURsjDA

MVT style JSON:
See ​https://www.openstreetmap.org/user/RobJN/diary/397365

MVT tile the above example appears in shows that it is not an issue in the source data as both postcodes appear within the tile data:
​https://api.mapbox.com/v4/robjn.3uur23nz/13/4091/2724.mvt?access_token=pk.eyJ1Ijoicm9iam4iLCJhIjoid0dYNkY1QSJ9.A-0lzQOawGYICYPfURsjDA

PNG raster tile layer (JOSM WMTS):
​https://api.mapbox.com/styles/v1/robjn/ckt38gru202nd18labo5bzds4/wmts?access_token=pk.eyJ1Ijoicm9iam4iLCJhIjoid0dYNkY1QSJ9.A-0lzQOawGYICYPfURsjDA&request=GetCapabilities

P.S In the raster tile layer the postcodes are just rendered on top of each other. Whilst this makes readability hard, it does at least show the OSM mapper than there is a conflict here to review. In QGIS the postcode labels are placed one above the other when I pass it the MVT data converted to geojson.

[Adrian]

I am the original user who reported this issue to Rob Nickerson. Below is my status report.

The ticket does not offer me the possibility of adding a Cc to taylor.smock but I think he should have a Cc.

Revision:18193
Is-Local-Build:true
Build-Date:2021-09-07 01:48:59

Identification: JOSM/1.5 (18193 SVN en_GB) Mac OS X 10.14.6
OS Build number: Mac OS X 10.14.6 (18G9323)
Memory Usage: 412 MB / 4096 MB (141 MB allocated, but free)
Java version: 16.0.2+7, Azul Systems, Inc., OpenJDK 64-Bit Server VM
Look and Feel: com.apple.laf.AquaLookAndFeel
Screen: Display 725375437 1920×1200 (scaling 1.00×1.00)
Maximum Screen Size: 1920×1200
Best cursor sizes: 16×16→16×16, 32×32→32×32
Environment variable LANG: en_GB.UTF-8
System property file.encoding: UTF-8
System property sun.jnu.encoding: UTF-8
Locale info: en_GB
Numbers with default locale: 1234567890 -> 1234567890

Plugins:
+ ImportImagePlugin (35567)
+ InfoMode (35543)
+ PicLayer (1.0.1)
+ apache-commons (35524)
+ cadastre-fr (35797)
+ editgpx (35562)
+ ejml (35458)
+ geotools (35458)
+ http2 (35427)
+ imagery_offset_db (35640)
+ jaxb (35543)
+ jts (35458)
+ log4j (35458)
+ measurement (35640)
+ opendata (35803)
+ photo_geotagging (35783)
+ poly (35640)
+ reverter (35732)
+ turnrestrictions (35640)
+ undelete (35640)
+ utilsplugin2 (35792)
+ waydownloader (35640)

[taylor.smock]

@rob.j.nickerson: Thanks for the feedback.

When I was originally implementing MVT support, I think I made the decision to reuse points whenever possible for memory reasons. I'll look into options for this -- it is probably going to be technically easy to change, but I'll want to check out the side effects.