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Just to be clear: Your data for the building heights, is that height above sea level, or height off the ground at said location? Since your units seems to be good--according to what you have said. Let us know. Just to reiterate, I once had to subtract the DEM heights from the building heights to get a true height for a project I worked on. Just making sure it is not something simple like this. Good luck.
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06-04-2012
08:50 AM
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Good Call thales007! Feet heights shown in meters just might look exactly like this.
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06-04-2012
07:54 AM
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Look into Least Cost Path. Remember just because the route is shorter does not make it best, What about the elevation of the path. Surely anything over 45 degrees is pretty hard to climb. What about a lake, how does that figure into the path. Yes these things can be done in ArcMap, usually they require a friction raster, easy to make but you have to understand what you are doing. Here is some work I have done: It addresses a lot of your concerns. Its a long copy paste but check it. Around Q 27 gets into logging trails and classifying those trails by using the shreve ordering system. Let me know if you want the data, I might be able to get it. 1 GRG 356T �?? Digital Terrain Modeling Lab 5 �?? Least Cost Path �?? Part I Objectives: the purpose of this lab is to show you the basics of least cost path analysis, using both cost and path analysis functions. We used least cost path functions in one of our hydrologic modeling labs. Here, you will use hydrologic functions in the context of path analysis. Report: Create your report in a Word processor, insert figures when necessary or when asked to, and submit through Blackboard on or March 28 th . Answer all questions marked with a �??Q .�?� Reminder: Beginning this lab, cartographic work will count toward your grade. Background 1: Suppose you are working with biologists that are studying animal behavior. They want to find the likely path a horse would take to get to a bale of hay. Your job is to use GIS and least cost path analysis to advise biologists about the likely path the animal will take. [Yet another silly topic for a lab but my purpose is to show that least cost path has a wide range of app lications, not only transportation analysis]. Instructions: 1. Create a Lab5 folder in your H drive; open ArcCatalog and connect to your folder. 2. Download the datasets from Blackboard and extract to your folder. 3. Open ArcMap and add the raster file nlcd92. Right click on this layer �?� Properties �?� Symbology �?� Import, and select nlcd92.lyr . This is a land cover map of a portion of Colorado in 1992. Q. Describe this raster. 4. Open the file nlcd92_code.txt using Wordpad. Q. How many strip mines cells are there? 5. Make a new grid of friction costs called friction by reclassifying [see more detailed instructions below] your land c over raster. Instead of having 13 different classes, I would simplify th e classes to 6-7. Assign friction values based on your own judgment. That is, do you think it would be easier for a horse to cross a pasture or a strip mine cell? For fun, make the one category really expensive (e.g. 100 for mines). 6. Q . Write down in the table below your fric tion values for each class. Include the table and a short justif ication in your report. Land Cover / Land Use Friction Value 2 7. To reclassify your grid, use the function Reclassify and enter the new values on the right. [Hint: click on the �??U nique�?� button on the right panel]. 8. Now, load the point file hay.shp. This is the hay bale location. You�??ll run the cost distance function. This is how you use it (of course, you should read the Help Menu as well): a. Source data: hay.shp file b. Cost raster: friction c. Output raster: accost1 d. Maximum distance: (leave blank) e. Backlink: bklink1 9. Q. Examine your accumulated cost grid (accost1). Use the contour function to create isocost lines (lines representing same cost). Check the (min, max) values to choose a reasonable interval. Comment on the general aspect of the raster. Make a figure with your contours. 10. Add your horse1.shp , which shows the initial location of the first horse. Now, calculate the least cost path. Click on Spatial Analyst �?� Distance �?� Shortest Path. a. Path to: horse1.shp b. Cost distance: accost1 c. Cost direction: bklink1 d. Path type: for each cell (since our house dataset is just a point) e. Output feature: lcpath1.shp 11. Q . Examine your results, comment on the path? 12. Now, add the location of the second horse (horse2.shp ). Since the origin (bale of hay) is the same, you DO NOT HAVE to recalculate the accumulated cost or back link grids (item 8). (Why?) Repeat only step (10) using your horse2 file. Make a figure (can include both horse 1 & 2 on same figure). 13. Q . How much will �??cost�?� horse 1 & 2 to get to the hay bale, according to your GIS analysis? 14. Add the DEM dem_co. Now, you�??ll use a more complex least cost path function called Path Distance. In this analysis, we will correct for the true distance based on elevation and correct for slope (i.e . upward slope is more expensive, downward slope is less expensive). Open the function �??Path Distance�??. Again, I will show you how to use it but you should also read in Help. a. Input source data: hay.shp 3 b. Output distance raster: accdem c. Input cost raster: friction d. Input surface raster: dem_co e. Output back link: bkdem f. Vertical Parameters i. Input vertical raster: dem_co ii. Vertical factor: Linear iii. Zero Factor: 1 iv. Low cut angle: -5.000 v. High cut angle: 5.000 vi. Slope: 0.2 (do you understand why it�??s 0.2?) g. Q : Draw a graph similar to this one from the Help menu, which is using the default values, but with your new vertical parameters Comment: the slope value parameter refers to the line slope of th e factor, not terrain slope. 15. Calculate the new least cost paths for horse1 and horse2 respectively using the cost path function. Remember to use th e new accumulated an d back link grids. 16. Q. Were there noticeable differences? In which parts of the landscape did you find noticeable differences? [Hint: you may want to calculate a slope grid, color code slopes smaller than 5% and see if th e path seeks low slope terrain]. Make a map. 17. Q. If you wanted to examine only the impact of the terrain on your path, disregarding the impact of friction valu es, how would you trick the function? You can try and see if there is any substantial difference between paths. 18. Remove all your files, EXCEPT your land cover and friction grids. 19. Add the file manybales.shp . Suppose now we have fi ve different locations the horses can choose to go. We are going to use a similar function to calculate an allocation raster in addition to your accumulated cost and backlink. Open Cost Allocation and use your manybales file as the source, your friction as cost raster. Name your allocation raster baleshed, your accumulated cost raster accmany and your back link grid bkmany. Q . Examine your new accumulated cost. 20. Q. Examine your baleshed raster. What does each allocation area mean? How would you interpret these zones? [Hint: easier to answer after item (22) 4 21. Add the file manyhorses.shp. Calculate the least cost path following (10) with new path to, cost di stance and direction grid. 22. Q . Make a figure showing the horses, the bales of hay, and the allocation grid on the background. 23. Q . What are the equivalent rasters for back link and allocation in hydrologic modeling? 24. Remove all files, except your land cover raster. 25. Background 2: Suppose now you�??re working for a logging company in the same area. Your objective is to design logging trails to access commercial trees and bring them to any part of the road infras tructure already in place, which will be your origin to the least cost path analysis. 26. First, you have to create a road raster . Use the con statement in the raster calculator and assign a value of 1 to class # 23 and no value data otherwise (remember, zero is a legitimate class). Name the output grid roads . 27. Create a new friction grid (see 6 & 7) but remember: your objective now is to minimize transportation costs. Is it cheaper to transport a timber log through a bare rock or grassland cell ? Name your new friction grid friclog. Q . Include the table below in your report and a short justification for your friction values. Land Cover / Land Use Friction Value 28. Calculate the accumulative cost and the back link grid; name them acclog and bklog respectively. 29. Load your trees.shp; this file shows the location of all harvestable trees. Calculate cost path using your trees as destinations and your accumulated cost and back link grids that you calculated above. Name output logtrails. 30. Now, we will calculate what is known as �??hauling traffic�?� raster. We will use the Shreve stream order classification from hydrologic modeling. But first, we have to reclassify your bklog to match the flow direction code (see below). Name new raster fdirlog. 5 Back Link Direction Code Flow Direction Code 32. Open the function �??Stream Order�?? and enter the appropriate rasters. Name output raster haultrfc and method Shreve. 33. Q. Read your lecture notes and review how the Shreve classification works. How would you interpret each road�??s segment number in your haultrfc raster? 34. Q . Suppose you are the logging operation mana ger. Which logging trail segments would require more maintenance? Why? 35. Q . Bonus (1 pt): There are similarities between hydrologic modeling and least cost path analysis. Water fl ows to the lowest point (ori gin in LCP) in your raster DEM following steepest descent rules (almost like following cheapest route in LCP). What raster in least cost path analysis would be equivalent to the DEM? Is it the friction, accumulated cost, or the back link grid? Explain your answer. Make a 3D figure in ArcScene to illustrate your answer.
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06-04-2012
07:49 AM
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I have not done much with regards to 3d analysis, but I recall that you may want to subtract the elevation/DEM from the building heights, that may be the problem. Perhaps someone who has worked more with this aspect can answer more thoroughly.
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06-04-2012
07:37 AM
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Thanks Dan for that clarification. Yes Fill would be the proper tool. Sinks will identify if there are sinks, and yes there are real world sinks, but they do mess up flow direction in ArcMap. For you to know if its a true sink IE a lake, you would need real world knowledge, on the ground knowledge. Thanks again Dan.
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06-03-2012
06:14 PM
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If its a brandnew laptop, it should be more than enough to run the Program. I ran arcmap on a singlecore with 1.5 gigs of ram which slowed it down quite a bit. At my university we used 2-core processors which ran okay. A new laptop with a multicore IE 2 , 3 , 4 cores should be more than enough. If you try setting the default database and it still doesnt work, I would try and contact some senior members on this forum, or contact techsupport if you have the ability. Wish you luck.
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06-03-2012
03:11 PM
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Okay I havent read the other posts, But if your flow direction is ANYTHING OTHER THAN the default values 2 4 6 8 so forth, then you have SINKS. Sinks are a basically errors in your DEM. The way to fix this is running the Sink tool on the flow direction raster. This will correct invalid flow directions. Let me know. Thanks.
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06-03-2012
02:55 PM
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What are your computer specs? Did you run the system prerequisite check before installing? Second thing. Kriging is very complex. Be sure to talk with someone who has done similiar studies on migration with kriging because there are several different ways to krig the same points and get vastly different results. You might want to check other peer reviewed articles that used kriging effectively. Just a suggestion. Be sure to experiment with several models, and pick one that matches the data that you have. If you computer has enough resources to run the program, and enough hard drive and memory, then it may be a simple fact of data preparation. Is the data projected? It needs to be if you are kriging((since kriging relies on the semivariogram and interpolation both which rely on correct distances)). I cant remember the maximum points kriging allows, but I do know the more points the better so feel good about that. There is a help button in the kriging tool, that will give you alot of information about kriging. EDIT:: If it turns out that you have enough resources, you are not using too many points, and your data is projected try creating a new geodatabase to store the output of the kriging tool. From my own experience, setting up the default database under environments saves alot of headaches in the longrun for sure. Setting this up is easy, just click add folder connection, click the new database icon in the brosing window, It has a star on a cylinder, and put that database where you are able to store it. Then go under Geoprocessing-environments ->>>>Select currentworkspace and browse to your new database. Hope this helps. Let me know.
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06-03-2012
02:41 PM
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Yeah, First, I dont know about taking Google placemark and inserting it---- It really just seems a matter of copying the lat long converting that to decimal degrees and creating an XY event layer in arcmap. as for the watershed: This is a multipart step. Download the DEM from USGS seamless viewer. its part of the USGS.gov website. Download the study area you are working with. Project the DEM. Open up the spatial analysis tools in the toolbox, open hydrology. (Im doing this off memory so...) Chances are there are errors in the DEM called SINKS. Okay from memory it goes something like this. Run flow direction. Then run Fill Sinks(just search for it) on the flow direction. Run flow accumulation. Then run the watershed tool. If you dont project the DEM, your results will be meaningless and incorrect.. If you can figure out how to do the steps I have written, you just might have it in you to get the job done. Good luck. If you are working on an area that the DEM is not readily available, I am not sure how you will get it. Many times the foreign countries other than the US charge for the DEM. Good luck again.
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06-02-2012
05:35 PM
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You could run the Euclidean distance tool, which will output as a raster file. Then run tool get attribute table (or something to that effect) which will create a table for the euclidean distance raster you just made. That is how I would approach it. From there I would figure out what else I needed to do to make a matrix happen. I am not sure if there are other ways.
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06-01-2012
03:49 PM
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Nad 83 is the datum, it is not projected you must project if you want anything meaningful from this. Project your data.
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06-01-2012
03:45 PM
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I have not taken graduate level statistics, but I do know that if your variables are linear, OLS regression is a good option. Furthermore, If the T-Statistic within the OLS regression comes back as significant, running GWR is the next step. If the T-statistic is not significant from OLS regression, You cannot justify running GWR. Hope this helps.
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06-01-2012
02:26 PM
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Yeah, There is a tool called fishnet, and another tool under cartography called create Grid I believe. Create a grid using the proper formula to determine cells size outside of ArcMap. Then once that proper cell size is determined, create a grid using the proper cell size. Once this is done. You can do a Spatial join, Or join by spatial location of the points to the grid cells. You can then clip the grid to the study area (or do this before). Hope this helps, let me know if I can be of further assistance. Good Luck
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06-01-2012
01:37 PM
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Yup the tech pretty much nailed it. Ripleys K and the blue line/ confidence envelope. This stuff is kind of advanced just so ya know. The blue line is based on a rectangular area. Therefore if the study area is not rectangular, I E an Island/Circular jagged etc, the points will only fall within your study area. therefore the blue line is irrelevant if you are using a confidence envelope. Run your analysis as if the confidence envelope IS the blue line. Any divergence from that, shows something that may not be random.
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06-01-2012
01:31 PM
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