LUPMIS - GIS User Manual for Land Use Planning

2.2 Digitize Line

Level of expertise required for this Chapter: Beginner

The standard process to enter lines to GIS is to digitize on-screen, with a background map (or the source) displayed on screen, and to follow each bend (vertex) with the entry device (mouse). The line begins and ends at so-called nodes.

Before you start digitizing lines in Map Maker from orthophotos or scanned topo maps, you have to load the source map in the background:
Right-mouse > Project manager > Add layer > Select file type (e.g. TIF or ECW) > Select folder and file > OK

Zoom in to the area of interest (by + and -), you can move around with the arrow keys (left, right, up, down). It is recommended to use to a very detailed level (see also Chapter 1.2 about navigation).

Start digitizing:
Line-tool (at toolbar left, or right-mouse > Drawing > Line) > Cursor changes to line with ‘Line’ > Start digitizing by clicking the mouse on each bend (creating vertices).

At the end of the line, you click the right-mouse > Line window: OK

You are ready to digitize the next line.

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If you like to modify a digitized line: Edit-tool (at toolbar left) > Double-click on the vertex (red dot), and drag it, or delete it. (See also Chapter 2.5 for editing).

If you like to move the entire line (‘dragging’, recommended only in exceptional cases), you can do so by moving the square at the right bottom to a new location (see Chapter 3.9 for full description).

After finishing all lines in that layer, you have to save it: Right-click (alternatively, main menu > Edit) > Save live layer > Accept DRA as file type > Select folder > Enter file name

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When you digitize a network, i.e. a road network, all lines have to ‘fit’ to each other: The end vertex point of one line has to be exactly (!) at the same location as the start vertex point of any other line(s). You can not do this just by moving the pointer to this location. You have to take one of the following tools:

A) ‘Snap vertex to nearest vertex’ after finished digitizing or editing the line: Line window or Edit vertex window: Actions > Snap vertex to nearest vertex > OK

B) If you have a new junction with a new road meeting an existing line,

it is easier to define an ‘overshoot’ (extend beyond the line to join) and then

Main menu > Edit > Show Selection Manager > Select-tool (at toolbar left) > Select the two lines to intersect > The Selection Manager window should show the two lines, like this:

Actions > Tidying > Tidy line junctions (spaghetti processing) > Tidy line junctions window: Snap distance: 0 m > Close gaps: 0 m > OK > X and

Select the ‘overshoot’ and delete

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Special option to digitize lines in Google Earth:

Before you start digitizing, you have to check, if Google Earth is installed, its resolution is good enough to recognize all structures and the horizontal accuracy is better than 10 m (for example, against the GPS). If these criteria are not met, digitizing is not recommended.

1. In Google Earth:

Load Google Earth > Zoom to area of interest (You can zoom in by +, out by -, move in all four directions (N, S, W, E) with the arrow keys. The indicated altitude should not exceed 3 km) > Add (1, see below) > Path > Google Earth – New window: Give name (2, see below) > Start digitizing by clicking the mouse on each bend, thus creating vertices.

If you like to change a digitized point, you can locate the point, and drag it to a new position. Afterwards, you have to click on the last point to continue with digitizing.
At the end of the line, you press Ok at the bottom >

> In ‘Places’ on the left side, you will find the newly created layer (under ‘My places’) > right-click > Save As … , or Save place as … > Save as type: KML > Select folder > Accept or rename file name > Save

If you want to edit a line after having finished digitizing, you click right-mouse on this track in ‘Places’ > Properties, and you are back to the editing mode. After having closed the line, do not forget to save it again as KML file.

2. With the software GPSUtility, convert KML file to SHP file. (See Annex 7 for utilities).

Load GPSUtility > License conditions for GPS Utility window: Yes (You can OK any other messages before that) > GPSUtility window: File > Open > Open window: Select Files of Type: Google Earth (kml, kmz) > Select folder and file > Open > Confirm window: Yes >

The imported data display should like this:

> File > Save/Export options > Save / Export / Print Options window: Select Format: Shape fileset (SHP+SHX,DBF)(1, see below) > Export As (2) >

> Save as window: Select folder > Specify file name > Check, that specified file type is still SHP etc > Save. Finished! > File > Exit

3. In Map Maker, convert SHP file to DRA file:
Main menu > Utilities > Vector utilities > Import file > ArcView Shape file > Step 1 of 3 window: Choose source SHP file > Select folder, file > Open > Next step > Step 2 of 3 window: Use serial number as object ID > Next step > Step 3 of 3 window: Choose target file > Select folder > Accept or change file name > Save > Finish > Confirm save

Finished! For checking purposes, you then download this file in Map Maker by:
Right-mouse > Add layer > Select folder and file (DRA file) > Open > OK. You should be able to see your digitized line. Then, Main menu > File > View in Google Earth, to see and check it with the original feature.

In Map Maker, you will, see if the imported line is in latitude / longitude or in UTM. If in lat / long, you must project it to UTM (see Chapter 5.2.4).

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Lines can also be added from GPS tracks. The tracking process is explained in Chapter 5.1.6, downloading in Chapter 5.1.7 (and 5.1.8).

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An interesting alternative, specific for entry of field survey with conventional methods, is explained in Annex 16.