Latest Contributions by PengGao3

With absolute building height, adding DEM surface does not solve the problem. I just tried that. I think this is because elevation values might be say 200 feet, while the building heights are 30 feet. Maybe I should add the elevation value to the building value before doing this? ... View more

Dan, Thanks for your input, which helped us to realize what we did wrong: First, we should do this in ArcScene, rather than ArcMap, though 3D analysis is still available in the latter; Second, for both buildings and points data, we should run a function 'Feature to 3D by Attribute' in 3D Attribute toolset. This will change both data from 2D into actual 3D data; Third, then we run 'skyline' using these two converted 3D data. This time, we could see the appropriate skylines generated. Some more comments/thoughts/queries: (1) the range of skylines is determined by the values in 'Virtual Surface Radius' (make sure to use the same unit as that in your data); (2) if you want to use the skylines to calculate skyline graph, then the range of skylines will not affect the calculation of angles; (3) currently, we simply assume that the base level of the point data is the same as that of the buildings, e.g., if the height of a point is 0, then it meanse the skyline from this point starts from 'ground' on which the buildings are based. We are not sure if this is a correct assumption. Also, this ignores the impact of terrain. We have DEM of the same area, but we are not sure if we use DEM to define 'Input Surface', how should we adjust the base level of both points and buildings. Should we simply add the elevations at their locations to points and buildings? I thank anyone who may provide some insight. Peng ... View more

Thank you very much!! The solution you provided is exactly what I am looking for. I will give it a try when I have time! ... View more

This is an important point to make. Your explanation is very thorough -- thanks. For my analysis, I need overlay effect, which means I need to use 'Focal Statistics'. ... View more

Thanks for letting me know. Just did it. Peng ... View more

?yes, it worked -- thank you ! peng ... View more

Not yet, but I just found that this might work. So, I will try it. Thanks a lot. peng ... View more

Sorry if I mass up your name. I mean you! Thanks again for your help. Peng ... View more

?Dan and Rebecca, It worked !!! Based on what you commented before, I suddenly realized one thing: the original values of the points are simply lat/long values. When I convert these values into points, no matter what 'correct' projection I will use, it will simply a 'suit' as one of you mentioned on the dog (the lat/long values). This is why the extent of my 'projected' point data shapefile is always based on original lat/long values. The other thing I tried before I posted my question was that when I do the conversion, I did not add any projection. Then, after I convert it into a point shapefile, I define it using the projection of the reference map. It did not work because I noticed that even if I did not add any projection, the extent of the point shapefile is still based on Lat/lomg values. Your comments make me realized one important thing: because the original values are lat/long values, when I convert it into a point shapefile, I should use GCS with appropriate datum! Based on the datum of the reference map, I learned that the correct datum should be NAD 83. So, when I convert the lat\long values into a point shapefile, I used GCS with the datum of NAD 83. After that, I use projection to convert the GCS coordinate system to the one associated with the projection of my reference map. This time, it worked!!! Many thanks for your help. I hope my summary may help others who have run into the same problem as I. Thank you again. You made my day!! Peng ... View more

I think you might be right. I have to go back to check how the lat/long data were obtained. Following is the screenshot. Note at the righ bottom, the unit is still degree though I have already defined the projection for this data. ?[cid:db6044ee-aebb-475f-b084-da05278875ff] ... View more