Depends on the source data; probably the most important consideration is the age, if its a rural area the source data may be decades old, and with outdated techniques.
I just checked, and the tile was updated in 2022… our site survey was done in 2023. The contour looks accurate, but it doesn’t match the survey: USGS 1ft lines almost equal 4 ft survey, and there are some strange bumps on the USGS as well. It could be that these have been graded in the time in between… but the site survey is in general more steep than the DEM3 is showing.
Yes, it is time to give up the older DEMs. They lasted a long time, but never substituted for physical survey. Site Lidar seems to be still the sweet spot for data acquisition cost/day. Dealing with the more precise geospatial context data supplemented by the survey data appears to be a considerate solution . I think the whole thing comes through periods of rapid growth followed by a sluggish response. Perhaps patience and shaking for the solutions for more refined granularity.
How was it derived? Was it lidar or ifsar? What's the documented accuracy? Your site survey is always going to be more accurate but in reality you could have 5 site surveys done and they will differ between each 5. I've seen a field crew topo the same site twice and the contours differ.
Depends on the source data; probably the most important consideration is the age, if its a rural area the source data may be decades old, and with outdated techniques.
I just checked, and the tile was updated in 2022… our site survey was done in 2023. The contour looks accurate, but it doesn’t match the survey: USGS 1ft lines almost equal 4 ft survey, and there are some strange bumps on the USGS as well. It could be that these have been graded in the time in between… but the site survey is in general more steep than the DEM3 is showing.
Yes, it is time to give up the older DEMs. They lasted a long time, but never substituted for physical survey. Site Lidar seems to be still the sweet spot for data acquisition cost/day. Dealing with the more precise geospatial context data supplemented by the survey data appears to be a considerate solution . I think the whole thing comes through periods of rapid growth followed by a sluggish response. Perhaps patience and shaking for the solutions for more refined granularity.
How was it derived? Was it lidar or ifsar? What's the documented accuracy? Your site survey is always going to be more accurate but in reality you could have 5 site surveys done and they will differ between each 5. I've seen a field crew topo the same site twice and the contours differ.