Frank Peng (2026-03-28 06:00:23+00:00): Just to make you aware, Bing aerial imagery of this location is distorted, causing Ellett Road and the VTTI Smart Roads Rural Roadway to appear to curve to the east from its actual alignment on the ground passing under the Wilson Creek Bridge (the high bridge carrying the VTTI Smart Road). VBMP aerial imagery of this location is more aligned with GPS traces, as it's orthoimagery, meaning there are little to no tilts in houses, buildings, structures, or other objects in aerial imagery; and no distortions in alignments of roads, paths, sidewalks, railroads, rivers, creeks, streams, and other land features in aerial imagery.

If you check Bing imagery of this location, you will see distortions in the alignment of Ellett Road and will find what appear to be squiggly curves on the road in Bing imagery, while the road does not actually curve like that on the ground. But if you check VBMP aerial imagery of this location, the alignment of the roads is more aligned with the GPS traces, and there are no distortions in the alignment of Ellett Road and the VTTI Smart Roads Rural Roadway in imagery, as VBMP imagery is orthoimagery. You will find said roads in line with their actual alignment on the ground in VBMP imagery. So when mapping in this area, I use VBMP Most Recent Imagery and set the imagery offset to "-0.67, 0.82" because VBMP imagery is offset by about 1 meter.

Before adding or moving OSM objects, it is important to check the GPS traces, as aerial imagery will, regardless of source, have offsets to the real positions of objects on the ground. While this can be small enough to be ignored, it can be substantially more than GPS errors and change over small areas. Per the "Good practice" OSM Wiki article, it states:

> Aerial imagery will, regardless of source, have offsets to the real positions of objects on the ground. While this can be small enough to be ignored, it can be substantially more than typical GPS errors (>> 10 meters) and change over small areas (requiring re-adjustment). It is mandatory that you check this before moving existing OSM data, or adding more.

https://wiki.openstreetmap.org/wiki/Good_practice#Align_aerial_imagery_before_tracing

We can check the actual placement of roads and other features by checking the GPS traces or tracks. Aerial imagery provides useful assistance in the mapping process, but it can be a bad idea to move map objects created by other mappers just to match them to aerial images. Aerial imagery may be distorted and shifted relative to real object locations, which is common in mountainous areas and hilly areas. Per the OSM Wiki article on "Using aerial imagery", it states:

> The exact placement of roads and other features can be assisted by recording GPS tracks on the ground. Aerial images clearly provide useful assistance in the mapping process, but it can be a bad idea to move map objects created by others just to match them to aerial images. Aerial imagery may be distorted and shifted relative to real object locations.

> Because there is, in any case (even if Earth was flat), perspective in the picture, objects may appear to skew to the side the higher above the ellipsoid they are, so this affects high-rise buildings, mountains, and roads going up/down hills. Perspective exists because the camera is only above one certain point at any time. The perspective problem can only be countered by taking more overhead pictures per distance, and combining them.

https://wiki.openstreetmap.org/wiki/Using_aerial_imagery

To check GPS traces in the iD editor:

* Click on the "Background Settings" icon (the layers icon) to the right (or press "B" on your keyboard) to display the right-hand "Background" pane
* Scroll down to the "Overlays" section
* If necessary, click on "Overlays" to expand the section to display the list of overlays on OSM
* Check the checkbox to the left of "OpenStreetMap GPS traces", and GPS traces will appear in the iD editor.