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Hello All I have a question about having 4 bounding boxes when Chicago has been set as central point. That is, I need four bounding boxes to divided world into 4 regions and the central point is located in Chicago, United State. I know how to acquire bounding boxes for country level but this is not what I need. Now, could anyone who helps me or gives me some suggestions about how should I start it? Thank you for your time and suggestion.
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10-15-2014
10:21 AM
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Hello all I am now working with so called "Big Data" and I found out that the maximum polyline features that GIS (I use ArcGIS10.2) can handle is about 20 millions. If there were more lines over 23 or 24 mllions, the ArcGIS would say: This features cannot be drawn (I also found out these error features cannot be created). Now, I just wonder if someone has such same situation or if someone who knows how maximum capacity that ArcGIS can work with? (Only for lines and points). I just want to make sure If I had any mistakes. This would be very helpful for me. Thank you.
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08-18-2014
10:52 AM
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Hello Thank you for your good presentation! I think this is a good way. But should I calculate the area of each polygon before working with Spatial join? Because I need compare their area.
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08-05-2014
07:32 AM
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Like what you said, I want to check how much it overlap each other and how it correlated (etc, one to one or one to many? or many to one?)I want to check how many polygons are matched from layer A to layer B and how. Here , taking a simply example as following (A1, A2,A3, B1,B2,B3 are polygons) Layer A (#30000: number of polygon) : A1 A2 A3 Layer B: (#70000) : B1 B2 B3 Because Layer A and Layer B are working with same region so that they have almost same city shape but their areas are different. That is, these two layers are somewhat different, which means A1 might not completely corresponding to B1. In this example, B1 might contain the sum of A1, A2, A3..... because layer B has more polygons (please note Layer A and Layer B are in same location). So, what I am going to do is knowing how do these two layer correlate each other (in terms of its city'area).
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08-05-2014
05:42 AM
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Hello Riyas I know that Union function can combine these two polygon files and obtain a new overlay area. But, do you have any idea how can area parameter can be correlated? I want to check thier spatial correlation. Thank you for your reply.
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08-05-2014
05:16 AM
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Hi everyone! I am now having a tough problem that I have any idea how to make a spatial correlation in ArcGIS. I just wonder if anyone could help me or give me some tips if possible. I will explain more details as following. I have two vector shpfiles, of which these two files are polygon. these polygon represent location of cities and size of cities in same region but different database. It means that these two polygons are somewhat similar.In terms of area of city, I would like to have certain spatial processing which can calculate its spatial correlation (not only size of cities but spatial correlation). I know spatial join function can make some spatial processing but dont know how does this function work with spatial correlation. In order to have a clear understanding,I will give a details example: For example, these two layer that I am going to work with are named as Layer A and Layer B. Layer A is a map of chicago and Layer B is also a map of chicago. However, the city boudary( size of certain polygons) of Layer A is little larger than the city boundary of Layer B(Also, some cities existed in Layer A might not be found in another layer,etc). Supposing if I make a Intersect function, They would have a overlay area that we can have both layers inside. Also, one Big polygon in Layer A might corresponding to two or even more small polygons in Layer B. I dont have much backround in such work so it would be very helpful if someone can kindly share his/her idea to this. Also,I would very happy if anyone can provide some new prespective. Thank you for your time
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08-05-2014
04:01 AM
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Hello I suggest that you could search some scientific papers and decide one direction that you want to work with. It is hard to say how does flood map can be defined. That is, You need to know what you need and how to get it. You could search related scientific papers in Google scholar and may get some ideas about how you can get your flood maps. In my opinion, Flood map refers to many directions and points, such as how we can define Flood map? how flood map can be mapped and how we can measure this flooding. So, just get this macro principle and then you will know what kinds of process you need to work with. Of course DEM data, flow direction and accumulation and stream network should be very helpful. Also, there were many tiny but important things during your processing, For example, How can you define your accumulation threshold and why this is important? So, read more papers and then you could focus on your technique part.
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07-09-2014
05:37 AM
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Hi all I have a point shpfile, which aims to use for creating TIN modle and TIN Edge. Then I will calculate the length of TIN edge. This point shpfie has many depulicated points. In order to correctly implement all process, I think it is necessary to remove all these duplicated points. However, I also found out that ArcGIS can also work with these depulicated points(Note: the number of depulicated points are huge, i.e 1-2 million). You can imagine if there were many points in same position, how can we get the length of TIN edge (actually, it should get 0 but not). Could someone tell me how does ArcGIS work if there have many duplicated points (regarding to working principle)? for example, Does ArcGIS can automatically remove this points or just record one points if there were mny duplicated points in one position?
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07-09-2014
02:14 AM
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Hi all I have a tough question about how value can be defined as a variable in expression (the function that I need to use is "Select by attribute"). To be specific, I have two-steps modelbuilder(which means I have to open the modelbuilder two times and then can get the result), the first step aims to calculate mean value and then use this mean value as a threshold value in the second step. Now, I want to make these two steps work together (as a one-step model). This is , I would like to combine this two modelbuilder so that I dont need to input this mean value every time. The ideal situation in my case would be like this: model can automatically calculated mean value and input as a threshold for second processing. In this case, I have to define this mean value as a variable, as this mean value is not constant but variable(Because I have too many works). Before this one-step model has been created, I have to type mean value manually as a input for the second step. For example, I obtained the mean value from the first step, for instance, 500, and then I make a expression : Features ?? 500. then all the features that are less than 500 would be selected. If I make this one-step modelbuilder possible, I could define this mean value as a variable , then I could probably make a query in expression, such as feature ?? value.mean? In this case, I dont need to know exactly what the mean value is, instead, I just use a SQL language and ArcGIS can automatically input every mean value calculated by first steps as a threshold for the second step. Note: I actually have two files in the second processing, one is this mean value table, another is one shpfile layer. I want to use this mean value as a threshold to acquire those required features from the shpfile layer. However, I dont have any background on SQL in ArcGIS and I just wonder if anyone could help me. I would be much appreciate. Please note the table calculated by the first steps was stored in one row, which means not all the value stored in table need to be used. Below is a format of table calculated by the first step. I only need that mean value. [ATTACH=CONFIG]35034[/ATTACH]
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07-02-2014
02:23 AM
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1. If it came from two independent sources it cannot be precisely aligned. Even a single source agency may be sloppy with this kind of topology. The different numbers from the methods you used show it is bad topologically. 2, The two methods are not equal. Polygons are harder to edge match than a it is to locate a point in the correct surrounding related polygon. One polygon equals one point regardless of size, so a single feature would never generate 2 points. The only question arises for multi-part polygons. If you break a multi-part poiygon into separate singlepart polygons then you have to track the source city ID for a count. In general extracting a single points with the inside option is all you normally would need, unless you have very gerrymandered boundaries. 4. The points method is my preferred method, but it requires an Advanced license, so other options have to be applied if you have the Basic or Standard license levels. Sorry, I forget one thing. You said Integrate function can help correct the features but how to set this function in ArcGIS. For example ,Should I input these two features together or put it separately.
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06-25-2014
10:48 AM
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1. If it came from two independent sources it cannot be precisely aligned. Even a single source agency may be sloppy with this kind of topology. The different numbers from the methods you used show it is bad topologically. 2, The two methods are not equal. Polygons are harder to edge match than a it is to locate a point in the correct surrounding related polygon. One polygon equals one point regardless of size, so a single feature would never generate 2 points. The only question arises for multi-part polygons. If you break a multi-part poiygon into separate singlepart polygons then you have to track the source city ID for a count. In general extracting a single points with the inside option is all you normally would need, unless you have very gerrymandered boundaries. 4. The points method is my preferred method, but it requires an Advanced license, so other options have to be applied if you have the Basic or Standard license levels. Ok, I will try and hope this can be helpful. Thank you
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06-25-2014
10:44 AM
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None of them are accurate. The two source maps will not match boundaries exactly where the two sources touch boundaries and as a result none of these methods will return a true answer. If the boundaries matched without crossing, then probably all methods would yield the same result. So the critical item is boundary alignment. As long as boundaries cross each other, Spatial Join is under-counting when you use the Contains option, while Union and Clip are over-counting small slivers of polygons. I would make copies of the source feature classes and use Integrate on them first to align the boundaries together better, then try the Spatial Join option with Contains. The number will likely increase. (Be sure to do Integrate on copies, not the original, since it directly alters the source geometry. You should always maintain an unaltered version of your original data unless the edits are verified before destroying the originals.) However, the real method I would use with an Advanced license is to first use the Feature to Point tool to extract the Inside point option of each city and then use Spatial Join to the points. Then use an attribute join of the points to the city polygons to transfer the country attribute. I might test the Multipart to Singlepart tool option before extracting the points to ensure they were centered inside each separate polygon part prior to doing the join and then performing a Summary Statistics to verify that each part fell in only one country before doing the join. If they did I would do the transfer. If they didn't, I would examine each that had a different Min and Max Country ID to find out how bad the overlap was affecting them. Getting exact counts is one of the most difficult tasks when data is poorly aligned. Several validation steps have to be done to verify that you have a correct result and manual intervention is almost always needed when the boundary alignment is very poor. Hello Sir Thank you for your kindly answers and suggestion. I also have some further questions regarding to your answers. 1. How do you know if one data is porrly aligned? Does this always happen or it is common? 2. You mentioned two methods to check, one was Integrate and another was transform polygon to points. Were these two are equal? if polygons are transformed to be points, do these point are reliable? For example, one big polygon might be split as two points then the number of cities (here is number of points) would increase. 4. I dont care if those points layer cannot be retun to be polygon since the only thing I need to know is How many cities are located in different countries. Which methods you prefer? This is very important to me and thank you for your kindly help.
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06-25-2014
07:04 AM
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Hi All I have a question about which geospatial process need to be selected in my case, I would be much appreciate if someone could guide me and tell me what their differences. I have two maps in my case, one is world bounday map (with COUNTRY name) and another is world city map(Only polygon without COUNTRY name). both maps are polygon formats. In order to know how many countries are located within certain country, I need use some geoprocessing tools, such as Clip, Spatial Join and Union. I just wounder which geoprocessing tools should be the best one if I want to link two maps and get the number of cities. I had already tried these three functions, see as following: Clip: I use cthis fucntion to clip those countries I need (According to the world bounday map by "Select by attribute") and output as a new file. Open the attribute table then the number of cities was there. Spatial Join: World bounday map is input as the Target features and World city map as Input featres. Then, "Contains" operation has been used for linking these two maps and result obtained. Union: Input these two maps and the output can also show the similar result as above mentioned. However, These three results are not equal in terms of the city numbers. For example, Clip could be 2000, Spatial join (Contains) could be 1850 and Union could be 1992. I have no idea which one will be more accurate. Please note: sometimes, some cities were located around the country bounday that may significantly affect the result of this geoprocessing since these cities might be counted. If anyone who has any experience on this topic, Please give me some suggestions and tips. Thank you.
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06-25-2014
02:09 AM
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Yes, instead of getting the statistics interactively, you can use the Summary Statistics tool Yes, that tool produces an output table. Yes, you have to look up the value of the MEAN for the field on which you requested statistics. A search cursor will do that quickly (there will only be one record). If you assign the value you have plucked from the table to a variable, you can use it in the subsequent where clause. You never mentioned using model builder before, so I gave you the interactive workflow. A Model Builder workflow will mirror the interactive one. Hello. Sorry for my miss mentioned. Could you please give me a simple example of how can that output mean value was defined or linked? if this is possible. Thank you ❤️
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06-20-2014
04:07 AM
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To get the average line length interactively, right click on the Shape_Length field in the attribute table and click statistics. let's say, for example, that the average is 5000 meters then you create a feature layer of the lines feature class, with a where clause: "Shape_Length" < 5000 You can make the layer interactively in ArcMap by adding that statement above as a Query Definition to the layer, or inside or outside of ArcMap by using the Make Feature layer tool and setting the statement as the where clause or Expression Now use the layer as the input to Feature To Polygon Only the lines of less than the average length (in our example, 5000 meters) will be used by the tool. Hello, I have a further question. You said the mean value was calculated by clicking stastisic. however, in modelbuilder, summary stastastisic can only calculate mean value through output a new table file. How can I connect to this table file? In my case, mean value is not a number rather it is a variable. for example, Shape_Length < table.mean (5000, 4000, 8000?). So.if it is possible to define mean value in table field? then this mean value can be used as a variable in Query definition?
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06-20-2014
12:48 AM
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