[Qgis-user] getting started for a complete GIS beginner
Hello all: Can anyone point me to an example of how to get started with QGIS? I was pointed to QGIS by a number of people who suggested it was an easy way to get started in GIS. So I downloaded it, and it works, but I still can't figure out how to do what I need to get done. I have an ESRI shape file for some town boundaries, and I have some data for those towns. I used the shape file to draw a nice map of the towns. It's all blue, and I don't know why yet, but it looks nice, and that's fine. But for the life of me I can't find the correctly shaped slot through which to slip the data I want to display. What I have is an ASCII (ok, UTF-8) table of data, with different scalar values for each town, and what I want is a map, with each town colored according to the values of the data. What do I need to do to get this data onto my map? What do I call this data in order to make sense of the manual? Do I need to start a PostGIS server somewhere? I only have a few dozen towns here. (I'm on a Mac, OSX 10.4.9, trying to use QGIS version 0.9, and the GRASS menus don't appear. I think I understand how I should have run things to see them, but don't know if that is essential for what I'm trying to accomplish. The relationship between GRASS and QGIS remains a little mysterious to me, and if enlightening me on that point will help me understand my problem, please do.) Because I've been browsing the archives of this list, I have to suggest that there are a couple of forms of help that I don't need. One is pointers to the QGIS manual, which I've looked at, and I'm sure is a great book, once you already understand the important concepts. For me, I'm beginner enough that I don't know whether the data I want to chart is (or should be) a vector layer, raster layer, a PostGIS layer or something else (none of them sound right to me), so I find myself unable to make any sense of the help in the book. I also don't need a pointer to a block diagram or general overview about how GIS systems work. At this point, I feel I could draw them in my sleep, but arrows pointing from data icons to little map icons don't address the problem I'm having which is where is the place to start learning about using this particular GIS system on my data? Many thanks in advance for indulging my ignorance on all this, -Tom -- tomfool at as220 dot org http://sgouros.com http://whatcheer.net ___ Qgis-user mailing list Qgis-user@lists.qgis.org http://lists.qgis.org/cgi-bin/mailman/listinfo/qgis-user
Re: [Qgis-user] creating a ellipse
Tim Sutton wrote: Hi Unless there is grass tool for doing this (havent checked), There's v.buffer. Will do just fine for buffering around points. However, doublecheck the results when buffering more complex shapes, polygons especially. It is agreed among GRASS devs that it would be easier to re-write v.buffer than fix it as it is currently. Volunteers welcome. Maciek ___ Qgis-user mailing list Qgis-user@lists.qgis.org http://lists.qgis.org/cgi-bin/mailman/listinfo/qgis-user
Re: [Qgis-user] creating a ellipse
Oh, and Nishith wanted an ellipsoidal buffer - in that case v.buffer won't do. I know Trevor Viens (can be reached him on GRASS lists) has developed an ellipse-enabled version of v.buffer, but I never saw it published. Maciek ___ Qgis-user mailing list Qgis-user@lists.qgis.org http://lists.qgis.org/cgi-bin/mailman/listinfo/qgis-user
Re: [Qgis-user] getting started for a complete GIS beginner
Hi, Tom, From what you've described as your immediate need (each town colored according to the values of the data) you don't need GRASS. Assuming you've got the attribute data associated with the locations, as described by Micha, then in Qgis, in the layer list on the left, select the layer of interest, then right click (or control-click) and select Properties. This will bring up a place where you can control the colors, or rather, select the method that Qgis uses to determine the colors. You want Unique Value in the Legend Type drop-down menu (in the Symbology tab of the Properties dialog box). That right-click thing also lets you open the Attribute Table, which is a place where you can see the dbf data from within Qgis. -Don At 12:20 PM -0500 11/26/07, tom sgouros wrote: Micha Silver [EMAIL PROTECTED] wrote: From what I read between the lines of your message, I gather that you have data in a text file, and a separate shape file of towns, with no connection between them. And you want to display the shape file in a map with each town appearing differently, depending on some data from the separate text file. Am I on the right track? Exactly the right track. Thank you for explaining how to get my data in place by editing the dbf file. Well, QGIS does not yet have any way to join between a GIS layer and a separate data file. All the data must be contained in the shapefile's table of attributes. This table is stored in a dbf Does that mean that I should just think of QGIS as a graphics package, meant for displaying geo data that is processed and joined somewhere else? Sort of a way to file the layers in a project and display the ones I need? Is the PostGIS connection only for getting vector and raster data into QGIS, a slicker way than reading a file, or is there something more you get from that connection? If that's right, can you help me understand what I get by adding GRASS? Many thanks, -tom file with the same name as the shapefile. (You might already know this: each shapefile is composed of at least 3 disk files: i.e. towns.shp, towns.shx and towns.dbf). You can open the shapefile's dbf part in a spreadsheet program like OpenOffice calc (or MS Excel), and then you can add additional columns (attributes) to the dbf from you ascii data file. Next copy-paste the actual data from the ascii file into the proper columns. I *highly suggest* you save a backup copy of the original shapfile dbf file just in case something goes wrong. That way you wan't loose your whole shapefile. Now open the shapefile with the edited dbf in QGIS and you will be able to use the data for displaying, labeling, etc... Cheers, Micha -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Tom Sgouros Sent: Monday, November 26, 2007 4:11 PM To: qgis-user@lists.qgis.org Subject: [Qgis-user] getting started for a complete GIS beginner Hello all: Can anyone point me to an example of how to get started with QGIS? I was pointed to QGIS by a number of people who suggested it was an easy way to get started in GIS. So I downloaded it, and it works, but I still can't figure out how to do what I need to get done. I have an ESRI shape file for some town boundaries, and I have some data for those towns. I used the shape file to draw a nice map of the towns. It's all blue, and I don't know why yet, but it looks nice, and that's fine. But for the life of me I can't find the correctly shaped slot through which to slip the data I want to display. What I have is an ASCII (ok, UTF-8) table of data, with different scalar values for each town, and what I want is a map, with each town colored according to the values of the data. What do I need to do to get this data onto my map? What do I call this data in order to make sense of the manual? Do I need to start a PostGIS server somewhere? I only have a few dozen towns here. (I'm on a Mac, OSX 10.4.9, trying to use QGIS version 0.9, and the GRASS menus don't appear. I think I understand how I should have run things to see them, but don't know if that is essential for what I'm trying to accomplish. The relationship between GRASS and QGIS remains a little mysterious to me, and if enlightening me on that point will help me understand my problem, please do.) Because I've been browsing the archives of this list, I have to suggest that there are a couple of forms of help that I don't need. One is pointers to the QGIS manual, which I've looked at, and I'm sure is a great book, once you already understand the important concepts. For me, I'm beginner enough that I don't know whether the data I want to chart is (or should be) a vector layer, raster layer, a PostGIS layer or something else (none of them sound right to me), so I find myself unable to make any sense of the help in the book. I also
Re: [Qgis-user] getting started for a complete GIS beginner
Don: Thank you again for your help (in my new neighborhood). I guess I somehow had the idea that data corresponding to a town *was* geo-referenced, since I also have the coordinates of that town's outline, and maybe that was where I was driving myself crazy. I understand the idea of editing the dbf file to get the data I want in there, and that certainly helps me begin to clear the air. But let me ask something else, since my task is simple, but I expect to have to do it quite often. The towns that I have are divided. Some are non-contiguous and there are lots of islands (I'm on the shore). Some towns make up twenty or thirty entries. There are only a few dozen towns, but nonetheless, editing the spreadsheet is more of a pain than it sounds (39 towns, 311 entries). I know that doing a join is possible in the spreadsheet, but it is, shall we say, somewhat inelegant, and like I said, this is going to happen a lot. Is this the GIS-approved way to go, or is there something better I could learn about? Say I have another pile of shape data, like zip-code outlines or census tracts. If I want to map those outlines to my town shapes, and come up with a list of zip codes or tracts that overlap each town, what would I use? I don't mind being pointed at something with a shallow learning curve, so long as I know that it will, in fact, have what I need somewhere up the slope. My problem so far has only been that from as far down here as I am, I can't tell what's on which slope. Again, I thank everyone for their indulgence of such basic questions. Thanks, -tom Don MacQueen [EMAIL PROTECTED] wrote: Hi, Tom, From what you've described as your immediate need (each town colored according to the values of the data) you don't need GRASS. Assuming you've got the attribute data associated with the locations, as described by Micha, then in Qgis, in the layer list on the left, select the layer of interest, then right click (or control-click) and select Properties. This will bring up a place where you can control the colors, or rather, select the method that Qgis uses to determine the colors. You want Unique Value in the Legend Type drop-down menu (in the Symbology tab of the Properties dialog box). That right-click thing also lets you open the Attribute Table, which is a place where you can see the dbf data from within Qgis. -Don At 12:20 PM -0500 11/26/07, tom sgouros wrote: Micha Silver [EMAIL PROTECTED] wrote: From what I read between the lines of your message, I gather that you have data in a text file, and a separate shape file of towns, with no connection between them. And you want to display the shape file in a map with each town appearing differently, depending on some data from the separate text file. Am I on the right track? Exactly the right track. Thank you for explaining how to get my data in place by editing the dbf file. Well, QGIS does not yet have any way to join between a GIS layer and a separate data file. All the data must be contained in the shapefile's table of attributes. This table is stored in a dbf Does that mean that I should just think of QGIS as a graphics package, meant for displaying geo data that is processed and joined somewhere else? Sort of a way to file the layers in a project and display the ones I need? Is the PostGIS connection only for getting vector and raster data into QGIS, a slicker way than reading a file, or is there something more you get from that connection? If that's right, can you help me understand what I get by adding GRASS? Many thanks, -tom file with the same name as the shapefile. (You might already know this: each shapefile is composed of at least 3 disk files: i.e. towns.shp, towns.shx and towns.dbf). You can open the shapefile's dbf part in a spreadsheet program like OpenOffice calc (or MS Excel), and then you can add additional columns (attributes) to the dbf from you ascii data file. Next copy-paste the actual data from the ascii file into the proper columns. I *highly suggest* you save a backup copy of the original shapfile dbf file just in case something goes wrong. That way you wan't loose your whole shapefile. Now open the shapefile with the edited dbf in QGIS and you will be able to use the data for displaying, labeling, etc... Cheers, Micha -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Tom Sgouros Sent: Monday, November 26, 2007 4:11 PM To: qgis-user@lists.qgis.org Subject: [Qgis-user] getting started for a complete GIS beginner Hello all: Can anyone point me to an example of how to get started with QGIS? I was pointed to QGIS by a number of people who suggested it was an easy way to get started in GIS. So I downloaded it, and it works, but I still can't figure out how to do what I need to get done. I have an
Re: [Qgis-user] getting started for a complete GIS beginner
tom sgouros wrote: Don: Thank you again for your help (in my new neighborhood). I guess I somehow had the idea that data corresponding to a town *was* geo-referenced, since I also have the coordinates of that town's outline, and maybe that was where I was driving myself crazy. What do you mean when you say you have the coordinates of the town's outline? Surely each town's outline must be hundreds of coordinates? I understand the idea of editing the dbf file to get the data I want in there, and that certainly helps me begin to clear the air. But let me ask something else, since my task is simple, but I expect to have to do it quite often. The towns that I have are divided. Some are non-contiguous and there are lots of islands (I'm on the shore). Some towns make up twenty or thirty entries. There are only a few dozen towns, but nonetheless, editing the spreadsheet is more of a pain than it sounds (39 towns, 311 entries). I know that doing a join is possible in the spreadsheet, but it is, shall we say, somewhat inelegant, and like I said, this is going to happen a lot. Is this the GIS-approved way to go, or is there something better I could learn about? Editing a shapefile's dbf using a spreadsheet is definitely *not* the GIS approved way. It was suggested as a quick and dirty fix for the problem you described. At first it sounded like: I have a nail and two boards. What tool can I use to connect them? But now it turns out you that you actually plan to build a house. So you'll surely want to resupply your toolbox! For example, to solve the towns on islands problem, GRASS has a module v.reclass, that can take individual polygons with some common attribute value, and merge them into a multipart polygon. However I'm not sure that's the proper approach here. If you merged all the islands into a single town feature, you'd loose the area and any other data particular to each individual island. You might best choose to give a town code (or town name) to each section that is part of a town, and use that code or name to link to a database table of other town data. This would most efficiently be done in PostGIS, of course. Say I have another pile of shape data, like zip-code outlines or census tracts. If I want to map those outlines to my town shapes, and come up with a list of zip codes or tracts that overlap each town, what would I use? I don't mind being pointed at something with a shallow learning curve, so long as I know that it will, in fact, have what I need somewhere up the slope. My problem so far has only been that from as far down here as I am, I can't tell what's on which slope. Again, these are spatial queries that QGIS alone can't do. The GRASS v.overlay module would do the trick. Dive in and try, and if you stumble over specific problems, come back and ask again... Again, I thank everyone for their indulgence of such basic questions. Thanks, -tom -- Micha Silver Arava Development Co, Sapir, Israel tel: +972(8)6592270 cell: +972(52)3665918 ___ Qgis-user mailing list Qgis-user@lists.qgis.org http://lists.qgis.org/cgi-bin/mailman/listinfo/qgis-user
[Qgis-user] more specfic help for a GIS beginner
Hello all: I believe my earlier questions have not been very well phrased. Here is my situation: I have an ongoing need to make a variety of maps of more or less the same kind. I have a small area, divided into 39 towns and about 75 zip code areas, for which I already have a dandy set of ESRI-style shapefiles. I have some data by town, and some data by the zips. No doubt I'll someday get data in some other package, too, like legislative districts or counties. The maps I want to make are pretty simple: color this town red if value X is over 12, and green if it's under. Color the town yellow if Y is also greater than 6. When I get data in the zip code areas, I'll need to re-jigger it into the towns somehow, so it can be compared with the other town data. This is a long-term thing, and I don't mind putting in the time to learn a new package. I'm not looking for quick-and-dirty solutions. But I am apparently very confused about what software is for which part of my tasks. I thought these were GIS tasks, and that QGIS was a GIS system, so it could do that, QED. (And the manuals I've read have been ambiguos enough that I couldn't resolve these questions there.) My questions: This is apparently not a QGIS thing. Is it a QGIS/GRASS set of tasks? Is there a way to run GRASS without QGIS, or am I supposed to think of GRASS as an extension to QGIS? Is some part of this best done with PostGIS? If so, which part, and do I use QGIS as the PostGIS client, or is there a better PostGIS client I should learn? Can I get print-quality (postscript is best) output from any of these systems, or does this requirement create restrictions I should know about now before I invest the time? Many thanks for your patience and assistance. -tom -- tomfool at as220 dot org http://sgouros.com http://whatcheer.net ___ Qgis-user mailing list Qgis-user@lists.qgis.org http://lists.qgis.org/cgi-bin/mailman/listinfo/qgis-user
Re: [Qgis-user] getting started for a complete GIS beginner
Tom, If you do some googling, you should be able to get to the point where you can ask less general questions. Some links below that may help you get started. Good luck. For translating some terms and concepts, this might be helpful: http://www-128.ibm.com/developerworks/library/os-gis/ For getting to know Qgis, you should look at these: http://gis.coaps.fsu.edu/FOSS_GIS/Introduction_to_Quantum_GIS_0_8_0.pdf http://www.geog.ucsb.edu/~jeff/gis/qgis_lab1/qgis_lab1.html http://blog.qgis.org/?q=node/86 Other tutorials and help documents you may want to look at: http://blog.qgis.org/?q=taxonomy/term/3 http://grass.gdf-hannover.de/wiki/GRASS_Help Best, John On Nov 26, 2007, at 6:34 PM, tom sgouros wrote: Micha Silver [EMAIL PROTECTED] wrote: tom sgouros wrote: Thank you again for your help (in my new neighborhood). I guess I somehow had the idea that data corresponding to a town *was* geo-referenced, since I also have the coordinates of that town's outline, and maybe that was where I was driving myself crazy. What do you mean when you say you have the coordinates of the town's outline? Surely each town's outline must be hundreds of coordinates? Yes, I meant the vectors of coordinates that are the towns' outlines. Editing a shapefile's dbf using a spreadsheet is definitely *not* the GIS approved way. It was suggested as a quick and dirty fix for the problem you described. At first it sounded like: I have a nail and two boards. What tool can I use to connect them? But now it turns out you that you actually plan to build a house. So you'll surely want to resupply your toolbox! Yes. The analogy is a good one. My problem is that everyone gives me manuals with words like soffit and stringer and fascia while I need a manual or tutorial that uses words like board and hammer. I'm sorry to seem so dumb about this (believe me, I am sorry), but I'm just having a hard time translating the abstract high-level ideas into the nitty-gritty of how do I actually do this. To be more concrete, I already know that what I need to do to make the maps I crave is to associate my town-level data with the towns in my shape files, and then map it. What I need to know, and what I haven't been able to glean from all the reference documentation that has been shown to me, is what software do I actually use to do that? Honestly, I thought that's what GIS systems are for, and QGIS is a GIS system, so I thought it followed logically that this is the kind of thing it does. But it isn't, apparently, so what is? other data particular to each individual island. You might best choose to give a town code (or town name) to each section that is part of a town, and use that code or name to link to a database table of other town data. This would most efficiently be done in PostGIS, of course. Hmmm. Of course? This may be obvious to you, but finding a way to understand what software does what part of these tasks is the whole point of my questions. I'll take this as a suggestion that perhaps what I need to do is to acquire some expertise making joins like these. Maybe I should start with PostGIS. In my blundering about with QGIS, I see that QGIS seems to have some a couple of dialogs that seem SQL client-like. Is QGIS the PostGIS client of choice for this kind of work, or is there some other client that is more complete or intuitive? Does PostGIS come with its own? Say I have another pile of shape data, like zip-code outlines or census tracts. If I want to map those outlines to my town shapes, and come up with a list of zip codes or tracts that overlap each town, what would I use? I don't mind being pointed at something with a shallow learning curve, so long as I know that it will, in fact, have what I need somewhere up the slope. My problem so far has only been that from as far down here as I am, I can't tell what's on which slope. Again, these are spatial queries that QGIS alone can't do. The GRASS v.overlay module would do the trick. Is this something you run via the GRASS buttons of QGIS, or do you run it separately? You say again. Do you mean that GRASS could do the data join I described above? Many thanks for your help and patience. -tom -- tomfool at as220 dot org http://sgouros.com http://whatcheer.net ___ Qgis-user mailing list Qgis-user@lists.qgis.org http://lists.qgis.org/cgi-bin/mailman/listinfo/qgis-user ___ Qgis-user mailing list Qgis-user@lists.qgis.org http://lists.qgis.org/cgi-bin/mailman/listinfo/qgis-user
Re: [Qgis-user] getting started for a complete GIS beginner
I think that the basic problem here is that QGis is GIS in development (note it is a 0.x version!), providing a good system for displaying and editing geospatial data (although there are few features still having to be integrated in the current version) and a python platform (a unique and promising characteristic of QGis that is perhaps overlooked by some users but that provides the basis for an extraordinary interfacing capability with other tools), but now almost completely relying on the raster-based GIS GRASS for any GIS analysis. The fact that QGis is not being able to do the join operation that you need is an strong indication that QGIS must have some analytical capability on its own, and actually this particular operation is a critical one, as you, on a purely user-oriented approach, have contributed to point out. The problem is that QGis developers cannot do everything at the same time and are now focusing on the display and edit tools, trying to get an stable version with no bugs. Putting pressure on them will just cause not having well finished tools. But I do think that the users must start to make a list of basic processing and analytical tools for QGIS. Without this (at least basic) processing and analytical capability, QGis cannot be considered really as a GIS. So, in fact, Tom is contributing to QGis development. Perhaps the current incompleteness of QGis as a GIS system should be stated on the web page along with a roadmap of its development. Getting back to your problem, in practice you have to: 1. Get your joining done in another software. 2. Make your display with QGis 3. Don't expect that tasks can be done while remaining in the ignorance. I do agree that we tend to abuse of jargon, and apologize, but you must get you some text book on GIS if you want to work in (or even with) GIS in the long term. One of the many things lacking in QGis are GIS tutorials explained using QGis tools, and it will take a while until we have them, I'm afraid. Agus tom sgouros escribió: Micha Silver [EMAIL PROTECTED] wrote: tom sgouros wrote: Thank you again for your help (in my new neighborhood). I guess I somehow had the idea that data corresponding to a town *was* geo-referenced, since I also have the coordinates of that town's outline, and maybe that was where I was driving myself crazy. What do you mean when you say you have the coordinates of the town's outline? Surely each town's outline must be hundreds of coordinates? Yes, I meant the vectors of coordinates that are the towns' outlines. Editing a shapefile's dbf using a spreadsheet is definitely *not* the GIS approved way. It was suggested as a quick and dirty fix for the problem you described. At first it sounded like: I have a nail and two boards. What tool can I use to connect them? But now it turns out you that you actually plan to build a house. So you'll surely want to resupply your toolbox! Yes. The analogy is a good one. My problem is that everyone gives me manuals with words like soffit and stringer and fascia while I need a manual or tutorial that uses words like board and hammer. I'm sorry to seem so dumb about this (believe me, I am sorry), but I'm just having a hard time translating the abstract high-level ideas into the nitty-gritty of how do I actually do this. To be more concrete, I already know that what I need to do to make the maps I crave is to associate my town-level data with the towns in my shape files, and then map it. What I need to know, and what I haven't been able to glean from all the reference documentation that has been shown to me, is what software do I actually use to do that? Honestly, I thought that's what GIS systems are for, and QGIS is a GIS system, so I thought it followed logically that this is the kind of thing it does. But it isn't, apparently, so what is? other data particular to each individual island. You might best choose to give a town code (or town name) to each section that is part of a town, and use that code or name to link to a database table of other town data. This would most efficiently be done in PostGIS, of course. Hmmm. Of course? This may be obvious to you, but finding a way to understand what software does what part of these tasks is the whole point of my questions. I'll take this as a suggestion that perhaps what I need to do is to acquire some expertise making joins like these. Maybe I should start with PostGIS. In my blundering about with QGIS, I see that QGIS seems to have some a couple of dialogs that seem SQL client-like. Is QGIS the PostGIS client of choice for this kind of work, or is there some other client that is more complete or intuitive? Does PostGIS come with its own? Say I have another pile of shape data, like zip-code outlines or census tracts. If I want to map those outlines to my town shapes, and come up with a list of zip codes or tracts that overlap each town, what would I use? I
