Data Layers in TileDriver

About Layers

The main purpose of TileDriver is to help you manage, process and visualize geospatial data. We refer to those data as layers.

A Layer is a discreet dataset containing structured data in some format as well as its associated metadata. In this sense, an image is also data: every pixel of an image may contain many data points, each of which can be manipulated using TileDriver.

TileDriver works with the following data types:

  • Vector
  • Raster
  • Velocity
  • Video
  • Web Map Service (WMS)
  • Tile Map Service (TMS)

The next few sections describe these data types and how TileDriver displays them in more detail.

Vector Layers

Vector layers consist of the kind of data you'd see in a spreadsheet: rows and columns. Each row is a record, each column contains a data value related to that record.

When you add a vector layer, the layer form looks like this:

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Vector output type

TileDriver can display vector data in a number of ways. The default is "Features," where each feature is drawn individually. Features may include points, lines or shapes. Other options include Hexbin and Heatmap. Each of these is described further below.

Features

As stated above, Feature layers may contain points, lines or shapes.

Points

When the Features layer contains points, TileDriver Visualize displays them in clusters based on their proximity.

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When you zoom in, the individual points become visible.

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Clicking a feature point displays the underlying data for that point.

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Lines

Feature lines display like this example of natural gas pipelines:

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Shapes

Feature shapes display like this outline of the Marcellus shale region:

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Hexbin

A Hexbin visualization is a way to analyze data in "bins," which are uniformly sized geographic areas. Here's an example:

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The purpose of binning data is to analyze relative concentrations of something, based on the quantity of measurements or some other data value. This particular example is showing the average heading of a particular type of boat in waterways along the East coast of the United States (if you're interested in this, you can download historic data from the Automatic Identification System here: https://marinecadastre.gov/ais/).

Heatmap

A Heatmap is another way to view relative concentrations, but with a more subtle variation:

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Choosing a vector output type

Basically, if you want to see the individual points in a dataset you should choose Features. If you want to use color to see data concentrations, Hexbin or Heatmap may work for you. Experiment! TileDriver Visualize has tools to help you enhance each of these output types to suit your needs.

Vector data file formats

At this time, TileDriver Vector layers only support the GeoJSON data format. If you need to convert your data, there are many tools that can be used. We recommend the open source application QGIS for exporting any vector data that you may have into the GeoJSON format.


Raster Layers

A Raster is a bitmap-type image, containing a grid of pixels. Rasters are contrasted with vector images which contain "paths" that can scale up or down as the image dimensions change (not to be confused with Vector layers).

Raster images are common in geospatial analysis. Many tools exist to take an aerial photograph, for example, and "ortho-rectify" it so that it can be correctly overlaid on a map. A pixel in an ortho image corresponds to some amount of distance on the ground; the higher the resolution of the photograph (often described in meters per pixel), the more detail you can perceive as you zoom in to the map. Many NASA satellites take 30-meter resolution images while photographs taken from the air can achieve 1-centimeter (.01 meter) resolution.

Certain cameras can take photographs that capture many wavelengths of light including those outside what we think of as the visible spectrum. Each wavelength is written to a "band" in the resulting image; in this way, a single pixel of a raster image can contain many (sometimes hundreds) of individual data points. If you're familiar with spreadsheets, think of every pixel as a row and each band of data as a column.

TileDriver lets you upload ortho-rectified images in GeoTIFF format. Here's what the layer form looks like when you upload a Raster layer:

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Once you upload a Raster layer, you can view it in TileDriver Visualize. Here's what one looks like, with some color-scaling based on the NDVI algorithm:

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As with Vector layers, TileDriver Visualize has tools to help you enhance Raster layers to suit your needs.


Velocity Layers

A Velocity layer is a special kind of Vector layer. Velocity layers allow you to visualize how particles flow through a regularly spaced vector field. They are useful for displaying things like wind currents (click screenshot to enlarge):

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Velocity layers must be uploaded in GeoJSON format.

You can view a great example of velocity layers in action on the awesome EarthWindMap site.


Video Layers

TileDriver has the ability to display ortho-rectified video files in .webm or .mp4 format. The screenshot below shows a frame captured from an airplane flying over a controlled forest fire.

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When uploading video files, you must enter the "bounding box" in lat/lon values as shown in this view of the upload form:

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Web Map Service Layers

WMS layers are provided by third party services like the National Map maintained by the US Geological Survey. When you add a WMS layer, the form looks like this:

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Note that when you add a WMS layer you don't upload a file. Instead, you enter a URL for the service and one or more layer IDs separated by commas. For example, if you wanted to display the Oak Ridge National Laboratory's Land Cover Map, you would enter the URL (http://webmap.ornl.gov/ogcbroker/wms) and the layer ID (10004_31). Here's what it would look like:

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The services that provide WMS data will publish the information you need on their websites (usually, sometimes you have to hunt around a bit).


Tile Map Service Layers

TMS layers are almost exactly the same as WMS layers; for TileDriver's purposes, the only difference is that you don't need a layer ID:

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