Mapping Met Office data in ArcGIS Online

Transcription

1 Mapping Met Office data in ArcGIS Online For non-commercial use only by schools and universities 1

2 Tutorial Overview In this tutorial, you will download and map Met Office data for the St Jude s Day storm on October 28 th The data can then be used to answer questions such as: Which weather station recorded the strongest wind speed? Which weather station recorded the strongest gust? What was the extent of the strong winds? Was it at a national or regional level? Skills By completing this tutorial, you will become comfortable with the following GIS skills: 1. Adding data into ArcGIS Online 2. Simple data editing in Excel 3. Mapping data as proportional symbols 4. Extension exercise Time Required The following classroom time is required to complete this tutorial: minutes All of the help documentation for ArcGIS Online can be found at: 2

3 Tutorial workflow Teacher Information A. Access Dataset Download data from Met Office B. View Attributes View the weather data and edit in Excel C. Map the data Add and map the data in ArcGIS Online D. Extension Exercise for experienced Excel users Map the dataset by wind direction with rotated symbols 3

4 Part A: Access Dataset In this section, you will download the data set and make some edits in Excel. 1. Click here to download the dataset. Note: This dataset was sourced from the Met Office: Through this link, you can download weather data in csv file format. To ensure that latitude and longitude coordinates are included in the download you must select Observational Data from the Query type search box, as shown below: As the data is downloaded in CSV format you can drag and drop the file directly into ArcGIS Online (not IE 7 or 8). 2. Open the data in Excel 4

5 In the Wind Direction column you will notice that a few of the cells will have the letters VRB and next to it in the Wind Speed column you will notice that there is a value of -99. The VRB is Met Office shorthand for Variable Wind Direction and this gives a no data value of -99 for the wind speed. These entries will affect the way ArcGIS Online maps the data so it is better to remove the whole data row from the table. In this example, there are 4 VRB entries to remove. Hint use Filtering in Excel to help you locate the rows that you need to delete. Once you have deleted the rows save the csv file. 3. Open your internet browser, go to and sign in with your public account credentials, using the SIGN IN button in the top right-hand corner. 4. Click the MAP link on menu along the top of the page to launch a new map. 5. Browse to the file location on your computer where the csv was saved. 6. Drag the file and drop it anywhere in the map viewer. You should see some points added to the map as shown below: 5

6 6

7 Part C: Map wind speeds as proportional symbols 1. Click on Change Symbols from the drop down list. 2. Choose Size in the Use box and select the same variables as shown below: You can edit the symbols by slecting Options and choosing Change All Symbols. Experiment with the different options shown below: 7

8 When you are finished click click Done and then Done Changing Symbols at the bottom of the screen. 3. Change the layer name to give a better description for the data field you have chosen by clicking the drop down next to the layer and select Rename Finally, you can your map to your content. Give the web map a title and appropriate tags. Tags are used when other users search for resources in ArcGIS Online. For example Storm, St Jude and UK could be entered as people will enter this if they are searching for this information. Part D: Interpret the dataset 5:00AM was chosen as it was publicised that the strongest winds at this time. We can now go back and answer the questions from the tutorial overview: 8

9 Which weather station recorded the strongest wind speed? Open the attribute table and perform a sort on the wind speed field. Which weather station recorded the strongest gust? Open the attribute table and perform a sort on the wind gust field. What was the extent of the strong winds? Was it at a national or regional level? This can be a visual analysis of the data. It can be seen that the south of England and along the west coast of the UK experienced high winds. You have now completed the Weather and Climate tutorial. Having completed the exercises you should now be more familiar with how GIS can be used to display geographic data with appropriate symbology. This allows the user to easily interpret data and also explore the interaction between different geographical features. 9

10 Extension Exercise for experienced Excel users: 1. Open the dataset you downloaded at the beginning of this tutorial. 2. Copy the following text into empty rows such as Y and Z: N 0 NNE 22.5 NE 45 ENE 67.5 E 90 ESE SE 135 SSE S 180 SSW SW 225 WSW W 270 WNW NW 315 NNW Your spreadsheet should now look like this: 3. Create a new field after the Wind Direction column and give it a suitable title such as Wind Bearing. 4. Enter the following syntax into the first row. Make sure that the syntax is set up correctly: =VLOOKUP(H2,$Y$1:$Z$17,2,FALSE) =VLOOKUP(H2,$Y$1:$Z$17,2,FALSE) 10

11 H2 = Value which will be converted. This should be the first row in the Wind Direction column. $Y$1 = the first column and row of the lookup table. This should have the value N in. $Z$17 = the last column and row of the lookup table. This should have the value 0 in. 2 = the second column of the look up table that will be used to replace the existing value. FALSE = only exact matches will be converted. The first row should now display the wind direction in degrees. 5. Click on the first row and then click on the bottom right of the cell to bring up the cross-hair. Drag down the column until you get to the last row. This should populate all cells with the wind direction in degrees. 6. Save your CSV file. 7. Back in your ArcGIS Online Map Viewer, drag the CSV file in again. 8. Click on Change Symbols from the drop down list. You will be given the option to symbolise your data in different ways. Use size to symbolise the points by and select the field Wind Speed. 9. Under Options, select Change All Symbols. 10. Select the Arrows category and select the second symbol and set the start and end sizes as they are in the image below. Click Done: 11. Back in the Change Symbols window, select Set Rotation Angle: 12. Select Wind Bearing as the field which holds to angles and leave the angles measured in a clockwise direction. Click Done: 11

12 13. You should now have a map that looks similar to the one below. We can now see where the strongest winds were but also their direction. 12