Marine Data Literacy 2.0

Providing instruction for managing, converting, analyzing and displaying oceanographic station data, marine meteorological data, GIS-compatible marine and coastal data or model simulations, and mapped remote sensing imagery

 

 

 

 

Home > 2. Marine GIS > 2.10 Text Spreadsheet

2.10 Adding a Text-Dominated Spreadsheet to a Project Map in Saga

 

1.  Download names_liberia_gns.zip to your folder DATA > BASEMAP > OTHER and unzip it in place.  Rename the file (probably li.txt) to names_liberia_gns.txt
2.  Run Saga.  Then load the World Borders dataset and make this map that zooms into Liberia.  We're going to add all the towns and cities for Liberia.

NOTE:  You can use 2.3 Creating a Project Map in Saga to get your map exactly like this.

3.  Select FILE > TABLE > LOAD. Then navigate to the file names_liberia_gns.txt and load it.
4.  Right-click on the new table object, and select SHOW TABLE.
5.  This table will appear.  Examine it to see what the field names are (i.e. the column labels).  You can compare what you find here with the format description, above.
6.  You should look carefully for any field names longer than 10 characters, the limit for shapefiles (which we want to make from this table).  Here you can see that several columns on the right side have oversized labels.

The easiest thing to do is to edit the names so they are all different, but only use 10 characters or fewer.

7.  Click anywhere on the line of labels in the table, and select RENAME FIELDS.  This window opens, where you can edit the names.  Make changes similar to these, keeping the fields identifiable but with only 10 letters or fewer.

Then click OK.

8.  The table contains nearly 9000 different features, of several different types.  We only want the towns and cities here.  The FEATURE CLASSIFICATION (= FC) column, gives us an opportunity to separate the different features, as you can see here, into types.  We only want the records coded with P.

How can we perform the separation?

Feature Classification (FC): Nine (9) major geoname feature categories into which similar feature designations are grouped.
A = Administrative region type feature
P = Populated place type feature
V = Vegetation type feature
L = Locality or area type feature
U = Undersea type feature
R = Streets, highways, roads, or railroad type feature
T = Hypsographic type feature
H = Hydrographic type feature
S = Spot type feature

9.  Select TOOLS > TABLE TOOLS > SELECT BY STRING EXPRESSION
10.  Make these selections:
  • Table - Select our place names table
  • Attribute - Select FC for Feature Classification
  • Expression - Enter P for Populated Places
  • Case Sensitive - Usually leave unchecked
  • Select If - Attribute is identical with search expression; unfortunately no negative choice is possible
  • Method - New selection; usual choice for single selection process

Then click OK.

11.  The table, if opened for view, now shows the selected records highlighted in gray, i.e. all those with FC = P.
12.  How to delete the other records, if we have selected only the P's?
13.  Select TOOLS > TABLE TOOLS > INVERT SELECTION.  Select the populated places table, then click OK.
14.  This switches the selected records to all the others, i.e. not FC = C.
15.  Now you can right-click anywhere along the left margin of the table and select DELETE SELECTED RECORDS.
16.  Now you can change the name of the table to populated_places_liberia-gns.
17.  You can also right-click on the table and use SAVE AS to save it in the folder PRODUCTS > SAGA > TABLES with the filename populated_places_liberia_gns.txt
18.  We need to convert this table to a "point shape" before we can do any further work with it.  Select TOOLS > SHAPES-POINTS > CONVERT A TABLE TO POINTS.
  • POINTS - Make sure you set it to CREATE, to avoid overwriting anything
  • TABLE - Select the name of the existing table names_liberia_gns
  • X - Select the LONG column (i.e. longitude)
  • Y - Select the LAT column (i.e. latitude)

NOTE:  we cannot use the longitude/latitude columns with the DMS (degree-minute-seconds) format, because all GIS work uses decimal degrees.

Click OK

19.  When the new shape appears, you can use SAVE SHAPES AS to save it in the folder PRODUCTS > SAGA > VECTORS with the filename populated_places_liberia_gns.shp
20.  Just for a reality check, here's what you see if you add the point shape to the Liberia project map.

This exercise cannot go into the difficulties of working with many place name labels, but we show you below how to display the names on the map.

21.  Too see some details, zoom into the very southeast corner of Liberia.

Here you can see the extreme eastern end of the country, after extreme zooming.

22.  In the properties window, find the DISPLAY: LABEL > ATTRIBUTE control and drop down the menu to look at the possibilities.
  • ATTRIBUTE:  Select the SORT NAME.

Then click SETTINGS > APPLY

 

23.  Here's how the labels appear.  You can explore FONT and size settings on your own at a later time.
24. Recent note from Saga author Volker Wichman about adding a data table with a date field:
  • When you load a comma separated (or tab delimited) table in SAGA, there are only three data types supported: strings, integers and floats
  • So you have to use quotes and the following format: dd.mm.yyyy
  • With the following table the date should be correctly recognize as data type string:
    id date
    0 "19.05.2015"
  • After loading the table to SAGA, you can use the "Change Field Type" tool to change the data type of the date field to "date".