Configuring the Scale Line

Configuring the scale line display is controlled via the application’s configuration object.

Example:

var app = new gm3.Application({
    mapserver_url: CONFIG.mapserver_url,
    mapfile_root: CONFIG.mapfile_root,
    map: {
        scaleLine: {
            enabled: true,
            units: 'imperial'
        }
    }
});

Valid values: * enabled - Boolean. true or false * units - String. 'degrees', 'imperial', 'nautical', 'metric', 'us' * printMode - String. 'none', 'line-distance', 'line-distance-scale'

The scale line on printed maps

When the scale line is enabled, the print dialog gains a Scale line option controlling what the printed map’s scale indicator shows:

Option	Shows
None	No scale indicator at all
Line and Distance	The bar, labeled with the ground distance it spans (e.g. 300 ft)
Line, Distance, and Scale	The above, captioned with the scale the map was printed at (e.g. 100 ft / in)

printMode sets which of these a print starts on; the user can change it for any individual print. It defaults to 'line-distance-scale'.

Once the user has seen the control, only the user moves it. If the selected mode stops being possible – picking a “Scale to fit” preset, which names no scale to caption – the dialog settles on the nearest mode it can offer and stays there. It will not quietly restore the caption later when a fixed scale is chosen again, because a print should match what the dialog last showed.

One consequence is worth knowing: the print dialog opens on “Scale to fit”, where a caption is impossible, so a printMode of 'line-distance-scale' settles to 'line-distance' on open. The caption is then something the user turns on after choosing a scale, rather than something they have to notice and turn off.

var app = new gm3.Application({
    map: {
        scaleLine: {
            enabled: true,
            units: 'us',
            printMode: 'line-distance'
        }
    }
});

Choosing a default is worth a moment’s thought, because the bar and the caption fail differently once the PDF leaves your hands. A scale in writing only holds for the page it was made for: a PDF exported at 1 inch = 10 feet and then reprinted at another paper size, or with the printer’s “fit to printable area” on, carries a caption that is no longer true. The bar is drawn on the page itself, so resizing the page resizes the bar with it and it goes on describing the map correctly.

'line-distance-scale' suits maps read on screen or printed at the size they were made for. 'line-distance' suits offices where PDFs are circulated and reprinted freely, and is the safer default when you cannot know how a map will be reproduced.

Note

The “Scale” option is offered only when the print can honor a scale: the “Scale to fit” presets name no scale, and a scale the map’s zoom limits cannot reach is left out rather than printed as a number the map does not honor. See Configuring Print Scales.

Setting enabled: false removes the scale line from printed maps entirely, and the Scale line option does not appear in the dialog.