Shape files are so-called vector databases, describing the location of points (e.g., collecting locations), polylines (e.g., roads) or areas (or polygons, e.g., soil types, countries). A shape file actually consists of three separate files with the same name but with different extensions (SHP, SHX and DBF), but they are treated as one file. ESRI, a leading GIS software company. They were initially developed for use in ArcView, but now nearly all GIS programs can either directly use them, or import them.
Shape files can be prepared with the help of any commercial software and also by some free software. Before going to the main tutorial a more detail concept of shape file is needed.
Shape file mainly consist co-ordinates and value/s attached. By far the most accurate representation of elevations is done with shape files. In this case co-ordinates and elevation of that point is recorded in the shape file.
For an example, try to answer the following question?
How can a man who can not read words but only numbers will find your house ?. The answer is simple: he will want to know the co-ordinates of your house. When you give the coordinates he can easily find your house. Now look into the following picture, how can you best describe the location of point ‘A’?
See Fig.1
If you assign the location of left – down corner as 0,0 then you can easily found the location of point ‘A’.
So, every point or points can be represented by co-ordinates. Shape files just store a value of parameters specific to that coordinate so that you can represent them graphically.
You will need 2 applicaions, 1 is completely free other one will cost you $ 450. First one is DIVA and later one is named as Surfer.
1. You want to measure the depth of a pond and represent the variation of them graphically on a digital photograph of the water body. Visit the field if possible or try to find out some depths of the pond(DEM is not considered as often resolution of those files are not satisfactory to make a bathymetry map).When you get this much data your next step will be to download Surfer and install it properly.
2. After you download and properly install Surfer, click on the Surfer icon to open the application.
3. From the top level toolbar select ‘Map’ and then ‘Base Map’.
3. Choose the pond map (this map image can be of any common image formats like jpg, gif,tif,emf) which you want to convert into shape file.
4. After you successfully import the file again click 'Map' and now select ‘Digitize’.
5. This digitize tool will help you extract the coordinate of the point on which you click. When you select ‘Digitize’ the curser changes to a + sign. Now click on any place of the digital image a note pad type of window will pop up with the co-ordinates of the point you click upon.
6. Click on the border of the pond after activating the ‘Digitize’ tool(Map > Digitize). This will give you the coordinates of the border. These co-ordinates are required to get the original shape of the pond.
7. Now that you have the co-ordinates of the border select the points for which you have the depths. Click 'Map' then ‘Digitize’ to activate. All this co-ordinates will be saved in a notepad (automatically).Save the file as Comma delimited CSV file. Open this file in an excel spreadsheet to write down the depths of those co-ordinates whose depths are known. For the border coordinates write the depth as zero.
6. Next go to http://www.diva-gis.org .Download DIVA-GIS.
7. If you downloaded DIVA from the Internet, you need to unzip the downloaded files
first (use e.g. pkzip; www.pkware.com). Then you should click on setup.exe to install DIVA; also click on this file if you are installing from a CD-ROM. You will be asked in
what directory (folder) you want to install the program. As you can install the program in any directory you like, in this manual we will refer to this directory as the. By default, DIVA will be installed in the C:\program files\DIVA-GIS\directory.
8. Click on ‘Data’ in the top most toolbar. Select ‘Import Points To Shape File’.
9. Select ‘From Text file’.
10. A pop up will appear. (See Fig).Click on the input button. Select the CSV file (Step – 7).
11.Tha data set in the csv will be now imported into bottom blank place(See Fig).Carefully monitor whether X column contain the Latitude and the Y column the Longitude. The last column will hold the values of the corresponding depth.
12. Click Output button and give a name to your shape file. Choose a location to save the file.
13. Click ‘Apply’
14. Your shape file will be created and saved in the folder you choose to save it.
15.As you have installed Surfer and if your only goal is to create the bathymetry map then no need to download DIVA, just import the excel file into Surfer. Surfer will ask you to choose X, Y and Z axis (which axis will represent what).It is better to place Latitude in X and Longitude in Y and Depth in Z.
16. Select the algorithm to get the unknown values of depth. Actually, when you create a graph with the help of Surfer it will try o find the intermediate values. For example the values of depth in between the co-ordinates say 2,4 and 3,5 are given.As you have not given the value of depth for co-ordinates 2.5,4.5 Surfer will automatically regress to get that value. I recommend using the ‘Radial Basis Function’ algorithm. This is, according to me, gives the best result than the other algorithms.
17. When you click ‘OK’ Surfer will create your bathymetry map. If you want to get a grid report then check the ‘Create Grid Report’ option on.
18. Remember to delete the unnecessary depths. Just double click on the graph (more precisely bathymetry map).A pop up will come up where you can delete or add depths (more precisely values of Z axis).Remember to give a – sign to your depth values. You can easily understand why?
Now that you have your bathymetry map as well as shape file it is upto you how you will start to use them.
Here is an example - two bathymetry maps - Back Side View and Front View(of a lake called Rabindra Sarobar in kolkata,depth measured by School of Water Resources,Jadavpur University,co-ordinates extracted and map created by Surfer) created by the above described method.
Shape files can be prepared with the help of any commercial software and also by some free software. Before going to the main tutorial a more detail concept of shape file is needed.
Shape file mainly consist co-ordinates and value/s attached. By far the most accurate representation of elevations is done with shape files. In this case co-ordinates and elevation of that point is recorded in the shape file.
For an example, try to answer the following question?
How can a man who can not read words but only numbers will find your house ?. The answer is simple: he will want to know the co-ordinates of your house. When you give the coordinates he can easily find your house. Now look into the following picture, how can you best describe the location of point ‘A’?
See Fig.1
If you assign the location of left – down corner as 0,0 then you can easily found the location of point ‘A’.
So, every point or points can be represented by co-ordinates. Shape files just store a value of parameters specific to that coordinate so that you can represent them graphically.
You will need 2 applicaions, 1 is completely free other one will cost you $ 450. First one is DIVA and later one is named as Surfer.
1. You want to measure the depth of a pond and represent the variation of them graphically on a digital photograph of the water body. Visit the field if possible or try to find out some depths of the pond(DEM is not considered as often resolution of those files are not satisfactory to make a bathymetry map).When you get this much data your next step will be to download Surfer and install it properly.
2. After you download and properly install Surfer, click on the Surfer icon to open the application.
3. From the top level toolbar select ‘Map’ and then ‘Base Map’.
3. Choose the pond map (this map image can be of any common image formats like jpg, gif,tif,emf) which you want to convert into shape file.
4. After you successfully import the file again click 'Map' and now select ‘Digitize’.
5. This digitize tool will help you extract the coordinate of the point on which you click. When you select ‘Digitize’ the curser changes to a + sign. Now click on any place of the digital image a note pad type of window will pop up with the co-ordinates of the point you click upon.
6. Click on the border of the pond after activating the ‘Digitize’ tool(Map > Digitize). This will give you the coordinates of the border. These co-ordinates are required to get the original shape of the pond.
7. Now that you have the co-ordinates of the border select the points for which you have the depths. Click 'Map' then ‘Digitize’ to activate. All this co-ordinates will be saved in a notepad (automatically).Save the file as Comma delimited CSV file. Open this file in an excel spreadsheet to write down the depths of those co-ordinates whose depths are known. For the border coordinates write the depth as zero.
6. Next go to http://www.diva-gis.org .Download DIVA-GIS.
7. If you downloaded DIVA from the Internet, you need to unzip the downloaded files
first (use e.g. pkzip; www.pkware.com). Then you should click on setup.exe to install DIVA; also click on this file if you are installing from a CD-ROM. You will be asked in
what directory (folder) you want to install the program. As you can install the program in any directory you like, in this manual we will refer to this directory as the
8. Click on ‘Data’ in the top most toolbar. Select ‘Import Points To Shape File’.
9. Select ‘From Text file’.
10. A pop up will appear. (See Fig).Click on the input button. Select the CSV file (Step – 7).
11.Tha data set in the csv will be now imported into bottom blank place(See Fig).Carefully monitor whether X column contain the Latitude and the Y column the Longitude. The last column will hold the values of the corresponding depth.
12. Click Output button and give a name to your shape file. Choose a location to save the file.
13. Click ‘Apply’
14. Your shape file will be created and saved in the folder you choose to save it.
15.As you have installed Surfer and if your only goal is to create the bathymetry map then no need to download DIVA, just import the excel file into Surfer. Surfer will ask you to choose X, Y and Z axis (which axis will represent what).It is better to place Latitude in X and Longitude in Y and Depth in Z.
16. Select the algorithm to get the unknown values of depth. Actually, when you create a graph with the help of Surfer it will try o find the intermediate values. For example the values of depth in between the co-ordinates say 2,4 and 3,5 are given.As you have not given the value of depth for co-ordinates 2.5,4.5 Surfer will automatically regress to get that value. I recommend using the ‘Radial Basis Function’ algorithm. This is, according to me, gives the best result than the other algorithms.
17. When you click ‘OK’ Surfer will create your bathymetry map. If you want to get a grid report then check the ‘Create Grid Report’ option on.
18. Remember to delete the unnecessary depths. Just double click on the graph (more precisely bathymetry map).A pop up will come up where you can delete or add depths (more precisely values of Z axis).Remember to give a – sign to your depth values. You can easily understand why?
Now that you have your bathymetry map as well as shape file it is upto you how you will start to use them.
Here is an example - two bathymetry maps - Back Side View and Front View(of a lake called Rabindra Sarobar in kolkata,depth measured by School of Water Resources,Jadavpur University,co-ordinates extracted and map created by Surfer) created by the above described method.
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