This is the latest incarnation of what used to be called the NTDB-Bugs Package, now renamed to Errata because in fairness only some of the errors documented here belong to the NTDB.It can be downloaded from http://renres.gov.yk.ca/pubs/rrgis/data/errata.zip
At present the Errata package consists of this document, an ArcView shapefile with database attributes, an ArcView project file and two older text files, and a document with pictorial examples.
At present the package only documents problems and changes with contours, waterbodies, watercourses, and digital elevation models.
The project file depends on a 30m shaded relief image catalog and the RRGIS data repository Arcinfo library setup for base data. If you don't have this only the Errata shapefile and database will load and you will have to manually add your base data.
We are sorry but the NTDB license agreement restricts us from distributing our corrected data so you will have to re-implement the changes described yourself. We do periodically send our corrected data along to the Land & Resource Information Management (LRIM) Committee who do have the authority do redistribute NTDB.
Important Note: The NTDB we have was recieved from LRIM, who translated the data from CCOGIF into ArcInfo coverages. It is possible some of the errors reflect not a problem with the source data but rather glitches in the translation process itself.
This web page is only periodically rebuilt, thus the shape and database files will always be more current than this page. A notice is posted on the RRGIS What's New page whenever any updates are published.
New contributions are welcome. Simply add records to the shapefile with a description of the errors and email to rrgis-tech@gov.yk.ca. Please preface the subject line with "Errata 50k:"
We lack the time and expertise to implement a proper bug database and automated patching mechanism. If anybody with those skills wants to take over management of the bug package, please do. :)
Most of the problems we've discovered can be traced to simple encoding errors. For example:
| wrong Z units specified | ~100 tiles had contours whose elevation units were feet while the metadata record said they were meters |
| wrong Z unit values | a small number of tiles contain contours with the wrong elevation values. For example halfway up a mountain slope the contours begin decending instead of ascending. Most of these are on tile borders, with the notable exception of 116J08 where the entire sheet was encoded in 10m intervals instead of 20m. |
| incorrectly joined streams | a single watercourse might go up one side of a mountain and down the other. |
| wrong thematic layer | a vector denoting the tree line is incorrectly encoded as a watercourse |
| wrong excode | the White Pass & Yukon Railway was coded as standard gauge while it is really narrow gauge |
The bugs package also describes changes we've made which can't really be called bug fixing. Most notable of these is:
| Z_metric | adding a Z_Metric attribute to the contour coverage so all tiles share a common elevation unit instead of some being feet and others metric |
| stream flipping | Watercourses have had their coordinate pairs ordered so that the first point in the vector element is upslope and the last downslope. Watercourses in low relief areas (braided streams & deltas) may not flipped correctly. |