POST
|
Hi Eric, It's old historical mapping - the topography has changed significantly since then, a modern DEM would be no good.
... View more
04-29-2013
04:16 AM
|
0
|
0
|
860
|
POST
|
Seems this is a tough one to do with any sort of thematic detail on the map. If the map is in colour, you have to convert it from RGB to greyscale before you can change the display properties to classified, so you lose some detial there. Then when you lower the number of classes to two, you lose lots more, particularly if there are thin contour lines. I tried selecting the contours in GIMP and then putting them in a seperate image, but the requirement for two classes only still caused problems. Any suggestions?
... View more
04-25-2013
01:14 AM
|
0
|
0
|
860
|
POST
|
I tried two really great tools this weekend, ArcScan and TopoToRaster. They do exactly what im looking for, but i would like to improve the results a bit. I downloaded a sample contour map off the net http://www.ducklakeproperty.com/images/map/Moon_Pond_detail.jpg then used ArcScan to make the contours into vectors giving me this image [ATTACH=CONFIG]23700[/ATTACH] im happy with it, even though i could probably tweak it a bit using the hole and gap settings - and then i run TopotoRaster giving me this greyscale DEM. [ATTACH=CONFIG]23701[/ATTACH] but as you can probably see, the levels are off..it is coloured as lower when it should be higher and vice-versa. I'm guessing thats because the vector contours i used had no elevation field? The manual is a bit unclear - it seems to imply the contours are all you need, but surely you need a starting elevation? Do i need all elevations? Any suggestions? Thanks, Conor.
... View more
04-22-2013
02:32 AM
|
0
|
5
|
2713
|
POST
|
that is really excellent - and the 3d/google earth is great for illustration purposes
... View more
04-21-2011
02:39 AM
|
0
|
0
|
559
|
POST
|
had a change of mind today, im using 'observer points' instead and it seems to be working alot better.
... View more
04-20-2011
07:10 AM
|
0
|
0
|
559
|
POST
|
Hi admahrou, Interesting blog post, and im looking forward to reading part two in the urban canyons, its similar to what im doing in a way. Yes, it will be GPS planning, but for urban areas. I had intended to get the details off the almanac, for GPS and Glonas at least. The transformation problem had occurred to me, but i hadnt thought it through properly, the issue of z values was causing me a bit of bother, because they would be so hugem i dnt know if arc will model them! What I had been planning was making a table with time as the primary key, and then xyz for each satellite. Then if you interactively picked apoint on a map, and a time, you could get LOS to satellites. Like I said, this has been done, but Im not sure how to go about using the LOS tool properly, and was hoping someone could help here. The current LOS tool seems VERY manual, and not easy to use with bulk data. For example in one of the papers I found, they wrote some avenue code Count = 0 for each aTarget 'possible observable satellite if (aTIN.LineOfSightsAsShapes (anObserver, aTarget, ListOfShapes) = True) then Count = Count + 1 end end Any suggestions?
... View more
04-20-2011
01:05 AM
|
0
|
0
|
559
|
POST
|
Hi All, Im looking at the LOS tool in 3d Analyst, and I'm trying to see if there is a way of modelling an observer point, their environment (buildings etc) and GPS satellites in orbit top figure out if someone would have signal or would it be blocked. I know it can be done, ive found at least three papers online by people did it. I have been experimenting in the office this morning but am a bit rusty on my ArcMAP. I have access to ArcMap 10 and 3d Analyst. LOS seems to work with a line between observer and target? This seems a pretty time consuming way of doing it. If i have to draw a line between each point, i could just as easily tell then if they were blocked or not. From the LOS dialog box.. "The input lines should be simple, straight lines with only two vertices each, representing observer and target positions" If i was trying to define a dynamic target, how should i go about it? Create a table with a an xyz representing each satellite position over a period of time? I would probably need to thin them down a bit, and if i included multiple satellites it would be quite computationally intensive... This doesn't need to be perfect, just a proof of concept for my owen benefit. Any ideas about where to go would be appreciated. PS - Somone told me recently avenue isnt used any more, what is used these days, python?
... View more
04-19-2011
03:39 AM
|
0
|
5
|
1181
|
Online Status |
Offline
|
Date Last Visited |
11-11-2020
02:23 AM
|