If you do not have the shape file of the area you are working on then you might have difficulty to create the polygon file that can be used to create the grid.
However, you can use the following tools to create the p2d file to use in EFDC Explorer.
The software / tools that are required for this process are as follows. All of the tools are free tools.
1) Google earth
2) KML CSV Converter
3) EFDC Explorer (WEB / TRIAL / FULL)
First of all, let us understand what are the data required to create the data. We required an outline of the water body for which we want to create the mesh / grid. In this case, we need the outline / polygon for the Lake Okeechobee. The easiest way to get the outline points is via the Google Earth. In Google Earth we can create a folder and create new place mark along the shoreline of Lake Okeechobee as shown in Figure 6.
Snapshot of Google earth showing the placemark along the shoreline of Lake Okeechobee
The second step is to output the coordinates of the place marks in Google Earth to real coordinates. We can save all the placemarks on one folder and save the folder as kml file. The saved kml file can be used in a third party application named “KML CSV Converter” and export the csv file as shown in Figure 7. Step 2 is completed after exporting the csv file from the application. The exported coordinates will have the Geographical coordinate system. In EFDC we need to use the UTM coordinate system. So, in third step, the GCS data will be converted into UTM data.
A snapshot of KML CSV Converter showing the longitude and latitude of the place marks in Google Earth
Step 3: Conversion of GCS data to UTM data:
There are several ways the data in geographical coordinate system can be converted to UTM coordinate system. Users can use ArcGIS or CORPSCON software to convert the data from GCS to UTM. Corpscon software can be downloaded from http://www.agc.army.mil/corpscon/ .
Snapshot of Corpscon Setup for the conversion from Geographic NAD (North American Datum) 1983 to UTM 1983
Alternatively you can use ArcGIS to change the geographic datum.
Step 4: Create the polygon file from the UTM coordinate data
In EFDC explorer, we need to provide the outline of the water body in the polygon (*.p2d) format. The steps 1-3 we performed to ultimately create a polygon file for the water body (Okeechobee in this case). The polygon file has 3 fields. The first field is X coordinate (longitude), second is y coordinate (latitude) and last is serial number which represents the data count. The first and the last points should be the same in order to ensure the polygon in closed. Figure 10 shows the format of the polygon file and it can be observed that the first and last points are the same. Looking at the data set we know that there are 22 points in the polygon.
Snapshot of the polygon data file to be used while creating the grid in EE.
Thus you can create the polygon file that you can use in EFDC Explorer.
Please write your comments if you have any other ideas.