Chart layers need attention

[signalk]

Chart layers need attention

[panaaj]

Commit #18853976343593548f33d7eb7b1863fd5b24dcd8 in #51 makes some changes to the way in which charts are displayed.
They are ordered in the chart list for selection by name but are ordered for rendering on the map by scale. Will need to confirm that the scale ordering (descending - largest scale rendered first) produces the the desired z-index ordering on the map display.

[tkurki]

Manual ordering might be useful as well as per layer opacity. Lots of GIS systems have this. Overkill maybe?

[rob42]

I had this in early freeboards. There is an ol layer widget that lets you hide layers. It is handy when you want to declutter, also when you want to get rid of a route or track.
Not a big thing tho.

[rob42]

In the chart list the chart is listed by name and description.
eg from this entry:

  "urn:mrn:signalk:uuid:14c2710b-3399-4a5d-9fba-aebb38c86483": {
    "identifier": "NZ29",
    "format": "png",
    "description": "Stewart Island/Rakiura to Campbell Island/Motu Ihupuku",
    "scale": 250000,
    "type": "tilelayer",
    "$source": "unknown",
    "maxzoom": 11,
    "name": "Stewart Island/Rakiura to Campbell Island/Motu Ihupuku",
    "bounds": [
      167.1332677218747,
      -55.99930283371544,
      176.53212338820407,
      -46.89919713462886
    ],

It would be better to include the identifier, which is typically used in external cruising notes.
eg
Currently:
Heading: Stewart Island/Rakiura to Campbell Island/Motu Ihupuku
Better:
Heading: NZ29 - Stewart Island/Rakiura to Campbell Island/Motu Ihupuku

This makes it easier to display chart NZ29 when referenced from a chart catalogue or pilot notes.

[rob42]

The rendering based on scale works properly. It assumes the scale is set on the chart resource, some sensible default would be good, eg just above base chart (openstreetmap etc).

Making layers visible or not by the chart panel works well enough not to need a separate visibility widget

[panaaj]

That's good to hear... I didn't have access to overlapping maps to test.
I'm not sure what a sensible default for chart scale might be (250000?) but can apply one easily enough.
I will make the change to the chart list heading as you outlined above also.

[rob42]

"Unselect All" would be nice. I have a long list of charts (all NZ charts) andscrolling down to unselect is tedious. "Select all" is not useful to me but might be good to add

[panaaj]

It's on Routes and Waypoints so I will add it to Charts also... it makes sense to be consistent.

• Charts now has a Select / de-select All check box
• A default scale of 250000 is applied to charts that do not have a scale value
• <Identifier - name> is now used in the chart list

[rob42]

You can see the effect here. The big blurry text is top of south Island, Next is Approach to Nelson, detail is Nelson harbour. The smaller scale charts show as you zoom in, and disappear as you zoom out, so no need to switch charts manually :-)

[rob42]

for default scale there are really 2 options.

1. Simplest - add it immediately above base map, eg z+1, maybe pop a warning?
2. Use bounds to calculate scale and apply...hows your geo maths? :-)

[panaaj]

1. If I make the default scale large enough it will end up at the bottom of the stack, the NOAA MBTILES I have been using to test have a reported scale (according to the charts plugin) of 250000.
   So a number of >250000 would be placed below these for example.

2. Not great.... Would it be reasonable to expect that given charts are served by some kind of TMS that a scale would be part of a valid dataset?

[rob42]

Most TMS servers would report scale, but I was thinking of drone photos :-) eg send up the drone (at low tide), snapshot the estuary or bar entrance, overlay on chartplotter! But then you would probably have set a scale along with bounds anyway, so not really a problem.

Formula for scale is https://stackoverflow.com/questions/29175701/calculating-scale-of-an-image, assumes bounds and dpi is known

Also found "Typical nautical chart scales range from 1:2,000 (sometimes referred to as “Berthing-scale” or a “Berthing chart”) to 1:10,000,000 (“Planning-scale”)." So maybe set as 10,000,001 ?

[panaaj]

@rob42 I have applied a default scale to any chart that does not report a scale in 1.0.0-0 pre-release on npmjs.com.

Can this issue be closed?