Can someone suggest a source for Canadian elevation data better or equivalent to 1 arc-second? I have a good data source for Ontario but for other provinces folks often recommend Geobase which claims that their elevation data ranges between 0.75 arc seconds to a maximum 3 arc seconds depending on latitude. However, I find that i cannot successfully generate shaded relief from the geobase data in ArcGIS. I've followed their instructions but the results are consistently un-usable. SRTM data from either cgiar.org or usgs.gov are good but I would like more detail.
Response from GeoBase:
Thank you for contacting GeoBase for a follow up on improvements to avoid 'stair stepping' effects found in certain CDED data sets. Presently there is no change attributed to the status of CDED specification requirements. CDED data originates from multiple partners and data sources which make it difficult to manage a homogeneous product throughout.
As you may now be aware the Z resolution in CDED files is causing the stair stepping effect. According to CDED specification standards for this scale, all elevations readings are rounded to the nearest meter of elevation for the entire Canadian coverage with approximately an elevation point every 23 metres by 16-11metres for the 1:50K scale. In flat areas, the rounding effect of the elevations causes homogeneous elevation plateaux instead of having a very gentle slope because the grid height values varies just a few centimetres. It's these adjacent plateaux that cause the stair stepping effect.
In certain cases some smoothing effect may be achieved by using the Focal Statistics tool in ArcMap Spatial Analyst toolbox, neighbourhood tools before processing CDED files. Depending on this software application you may be able to adjust viewing features with the tool menu for '' Neighbourhood=Circle, Radius=5, Units=Cell and Statistics Type=MEAN''. But I don't think there is a perfect setting for all CDED files. There is a part of trial and error in the settings for each tile. Because of this situation and the software you are using you may need to request assistance for your software provider to smooth out the look of you files. Because no perfect solution was arised from our tests, GeoBase did not provide a universal user guide for smoothing out CDED elevation data, in the Frequently Asked Question segment.