# Luna

Kx Luna is a high-performance temporal geospatial visualisation component.

## Features

• High-performance 60FPS/120FPS rendering of both temporal and static geospatial data
• Multiple layer rendering types and customisable presentations:
• Points
• Polygons
• Video

## Properties

### Luna

Title / Subtitle
Optionally set a Title and Subtitle (shown in the bottom-left of the map)
Time
Time field sets a Float . This value can be set to a viewstate, Luna will update this View State when the time-slider changes.
ILatitude / ILongitude / _IZoom
Sets the initial load for the Latitude, Longitude and Zoom
Latitude / Longitude / Zoom
Tracks the current Latitude, Longitude and Zoom values

### Layers

Multiple Layers can be displayed on a Luna Map

Enabled
Toggle the display of the Luna Layer
Name
Set the Name to a name that will be shown on the map (presentation only)
Type
Set the Type to the relevant Layer Type
LayerID
Set the LayerId to match the .luna file in the Luna Registry (no extension)
Args1
(optional) limit on the number of slices to load. This allows you to load a subset of available slices, useful for reducing load time when debugging.
Arg2
(optional) Icon, which can be: A Font Awesome Free v4 Icon Name and optional colour e.g. fa-car green. A relative path to an image file e.g. circle.png (relative to /modules/Luna/luna/assets/) or Empty, which will use the default icon (dot.png)

Info

Cables luna files demo built into application

• Name: Undersea Cables
• Type: LineSegment
• LayerId: cables.luna

## Developing a Layer

Luna Layers are composed of :

• Packed-binary .luna file(s) containing one or more temporal vectors, which may represent X,Y co-ordinates across time or other representations

Example

UVs, colours. For larger temporal layers there may be a set of .luna files, typically each will represent 1 time-slice (a “slice”).

• A .meta file containing JSON metadata definitions of the contents of the .luna file

Layers are “baked” offline using kdb+ and luna.q, typically from a source table containing time,latitude,longitude columns. The .luna files are downloaded as static assets by Luna running in the browser, hosted as a component inside of Kx Dashboards.

Your source table must contain at least the following columns:

• time (timestamp)
• id (long)
• lat (real)
• long (real)

Each row should represent a single object’s positional co-ordinate in time (but you do not need to represent all Thing’s each every timestep).

The id of your objects must be sequential and contiguous (no gaps), if it is not you should map your id’s to a sequential counterpart using

Example Query

df:update id:((distinct dfVehicleId)!(til count distinct dfVehicleId))[VehicleId] from df;

You should snap your times to a regular cadence (e.g. update time:0D00:00:30 xbar time from df) so as to limit the total number of slices.

You are limited to a maximum of 9,999 slices (however this is an arbitrary limit and only relates to download time of so many individual slices for Raw layers)

## Generating Layer Data

### Layer Type: Raw

Raw layers are able to encode large volumes of encoded temporal position data and may span thousands of files, each representing an individual timeslice. These can be directly loaded by the Luna frontend from static asset files on disk.

To generate the layer data (using luna.q):

q) layer:.luna.table2layer_raw[table]


This function pivots your table in the following way: - Each row is a specific timeslice - Each row represents all objects positions (projected lat,long) at that timeslice The function returns a layer dictionary containing metadata about the layer, and layer data. It does not alter the source table.

## Saving a Layer to Disk

To save the layer output by .luna.table2layer_raw to disk:

q) .luna.layer2disk[$"walks/telewalk";layer]  Each row (timeslice) is output as a separate sequentially named file e.g. walks/telewalk_512x64x8_0000.luna walks/telewalk_512x64x8_0001.luna Info The filename naming convention for Raw layers (which lack a .meta) is important as it encodes the total slices (e.g. 512), width (64) and height (8) dimensions of the layer buffers. ## Deploying a Layer The .luna files (aka “Layers”) are static assets/files, and are retrieved by Luna from the URL: https://.../modules/Luna/luna/assets/layers/xxx.luna Your .luna files should either reside within the Kx Dashboards deployment in e.g.: dash/www/modules/Luna/luna/assets/layers/ If the kdb+ instance where you are saving out your layer resides on a different server or path to where your static assets are delivered (from e.g. nginx) you will need to manually transfer the files to that location, in order for Kx Luna for Dashboards to download it. Alternatively, use an nginx reverse proxy “fronting” Kx Dashboards to intercept the above URL and serve the static assets from another location on disk using the following nginx.conf:  server { listen 8443; server_name luna.na.nu; gzip on; gzip_types text/plain application/xml application/json; location /modules/Luna/luna/assets { alias /nvme0/kx/kx-luna-assets; } location / { proxy_pass http://127.0.0.1:10001/; proxy_http_version 1.1; proxy_set_header Upgrade$http_upgrade;