Ticket #759 (closed bug: wontfix)

Opened 2 years ago

Last modified 1 year ago

Whitebark pine data error

Reported by: guest Assigned to: somebody
Priority: major Milestone: Sprint 5
Component: GUI Version:
Keywords: Cc:
Estimate:

Description

I wanted to produce a map of whitebark pine distribution in the ESSFmk area of west central BC. I was disappointed to not find whitebark pine on the list of species because I know that Pa (Pinus albicaulis) appears on the VRI forest cover label. However, it occurred to me that I could use the "Pine, Not Lodgepole pine" approach to narrow down my query. The resulting map looked quite reasonable as the red squares were located in areas where I know that Whitebark pine is common. However, when I clicked in the data for a particular hectare it indicated Pine No, Lodgepole Pine No and lower down in the Tree species description it indicated that the polygon had Hemlock as the leading species and Balsam as secondary species.

Change History

08/19/09 09:02:35 changed by egouge

* Whitebark Pine Whitebark Pine exists as a part of the "Pine" species. The metadata for "Pine" says that that species includes: PA (Whitebark Pine), PF (Limber Line), PJ (Jack Pine), PM (Monterey Pine), PW (Western White Pine). Unfortunately this probably doesn't help you if the only thing you are interested in is Whitebark Pine. Currently, you won't be able to get to this level of detail. The species groupings that are shown in the layer tree were determined in consultation with our ministry of forests contact at the time we were processing the data. We may need to revisit this if there is a consistent demand for the individual species.

* The discrepancy you see between the map and the "info" tool. This is a bit more complex and is likely a result of the zoom level you were viewing the data at and the way the VRI data was processed. I will attempt to explain.

The VRI "Species" layer consisted of a set of polygons where each polygon had up to six species each with a given percent (ie. Polygon A is 40% Pine, 60% Cedar etc.). We couldn't represent data like this well in Hectares BC so the way we approximated this data was to assign "Pine" to 40% of the hectares within Polygon A and Cedar to the other 60%. If the zoom in and ask for pine you'll see a checkboard effect where approx 4 out of every 10 pixels are red (the assignment was done randomly so it won't be exactly 40%; however it is close). If you aren't zoomed in all the way you likely won't see a good representation of the checkboard effect because of the resampling that occurs.

When you use the info tool it may look like you have selected one of the hectares that matches your query, however if you zoom in you may see that it actually doesn't. This is likely the cause of the issue you describe above; however without a few more details about the zoom level & hectare that was clicked I can't be sure.

08/10/10 15:01:24 changed by egouge

  • status changed from new to closed.
  • resolution set to wontfix.