Visualization options

Color ramp

The color scale used for %RE (percent relative emission) in the 3D and 2D views. Plasma, Viridis and Inferno are perceptually ordered scientific colormaps: low response reads as a dark color, high response as a bright one. Turbo is a rainbow-like scale, easier to tell levels apart on but harder to read in grayscale or with color-blindness.

The color scale runs from the transparency threshold (the bottom label on the colorbar) to the highest estimate on the job's grid (the top label). Its labels are %RE values, so “150%” on the colorbar means 150 %RE. The top usually differs a little from the highest reading in the boring logs, most often lower; see what is measured and what is estimated.

Transparency threshold

Any interpolated %RE value at or below the transparency threshold is drawn fully transparent, in the 3D and 2D views and in the GeoTIFF export. Use it to hide background response. The default, 2 %RE, is below the background of most UVOST logs (the Example Job's perimeter borings read up to about 6 %RE), so at the default the colored area includes background, not just contamination. Raising the threshold to your site's background level shows the plume itself, so the results page opens at twice the site's background, taken as the median of every reading in the job (most of any UVOST log is background, even in a hot boring): 7 %RE on the Example Job. The viewer files in the download, opened on their own, start at the job's own threshold. Drag the slider for a rough setting, or type an exact value in the box beside it; both run from the job's lowest estimate to its highest. For example, the histogram below shows the values on the Example Job's grid; a threshold of 5 %RE hides the low end of the distribution, making the higher-response areas easier to see.

Transparency ramp shape (Gamma value)

Above the threshold, each value is drawn between fully transparent (at the threshold) and fully opaque (at the highest estimate). The Gamma value sets the shape of that ramp. Take how far a value sits between the threshold and the highest estimate, as a fraction from 0 to 1: its opacity is that fraction raised to the gamma value. A negative gamma uses one over the value instead, so −2 gives the same curve as 0.5.

Positive values (e.g. 2, 3) fade out all but the strongest response, for a sharper, more solid hotspot with a thinner halo. Negative values (e.g. −2, −3) do the opposite, keeping faint, near-threshold response visible. A value of 1 or −1 is a linear ramp, where opacity rises in direct proportion to %RE; that is the 3D view's default.

Gamma value / Threshold plot examples

Gamma value: 2D vs. 3D

The 2D and 3D views each have their own, independent Gamma value — moving the slider on one tab does not change the other, and switching tabs re-shows whichever value that tab is currently set to. This is deliberate: the same gamma number produces two genuinely different-looking results in the two views.

This is because the 3D viewer draws the plume as many small, partially transparent glyphs, and the gamma value on the slider affects each individual glyph. From most viewing angles, you are actually looking at many glyphs "stacked" on top of each other. The result is that many individual glyphs are blended together to form a color and transparency that appears much more opaque than any individual glyph. The 2D plan view has no such stacking effect — it shows the single strongest %RE value found at each location, colored by that one value alone (see the interpolation methodology page for why it's the max, not an average). So at the same gamma value, the 2D view shows a single object while the 3D view shows dozens of partially-transparent copies stacked on top of each other. This is why the 3D view appears far more solid for what is, numerically, the same setting.

To compensate, the 2D view starts at a much more aggressive default gamma (-5, boosting faint response heavily) than the 3D view typically uses, so a freshly-opened 2D view reads closer to what the 3D view already shows. This is a reasonable starting point, not an exact match — a single gamma curve mathematically can't reproduce the shape of ~70 stacked, blended glyphs (notice in the chart above that even the boosted 2D curve still falls short of the 3D curve especially near the threshold) — so feel free to keep adjusting the 2D tab's own Gamma slider from there until it looks right for a given site.

Can a setting hide contamination?

Yes. These controls change only what is drawn, but what is drawn is what a reader of your figure sees:

• Everything at or below the transparency threshold disappears from the 3D and 2D views and the GeoTIFF export.
• A high gamma fades moderate response almost to nothing. At gamma 3, a value halfway between the threshold and the highest estimate is drawn at one-eighth opacity; on a site with one very hot boring, that can be a 200 %RE zone.
• The color scale tops out at the job's highest estimate, so one very strong boring makes everything else look dark and faint.

The contour lines in the 2D view and the shells in the 3D (Isosurface) view are drawn at fixed levels (10, 25, 50 and 100 %RE) and are not affected by gamma; the contour lines also stay drawn whatever the threshold. They are the safest way to show extent. When you use an exported image in a report, state the threshold and gamma in its caption, and that the colors are estimates between borings, not measurements.

Glyph size

The 3D plume in the interactive viewer is drawn as a cloud of many individually-colored glyphs (small shaded spheres, one per interpolated location), not a solid surface. Each glyph is sized in on-screen pixels, not real-world units — so the same glyph size can look perfectly smooth at one zoom level or boring layout and show visible gaps at another, since a fixed pixel size covers fewer real-world inches the closer you zoom in. The app automatically picks a sensible starting size for your specific data, but if you ever zoom in and start seeing a gapped or checkerboard-like pattern, drag this slider up until it smooths back out — or drag it down if a hotspot looks overly soft or bloated for your liking.

This only changes how the existing data is drawn, and only in the 3D viewer — every interpolated location stays part of the same underlying data, with the same %RE value, no matter where this slider sits.

Contour lines (2D)

The 2D plan view can draw contour lines (isopleths) at 10, 25, 50 and 100 %RE, each labeled with its level (“25%” on a line means 25 %RE); a level the site never reaches is left out. Every level stays drawn whatever the %RE threshold, so as you raise the threshold the lines still show the shape of the plume beyond its colored part. The lines are traced on the kriged grid and gently rounded. They are solid between the borings, inside their footprint, and dashed in the extrapolated area past it. Where the colors stop, so do the lines (see how lif-viz decides which estimates the borings support). Untick Contour lines to turn them off; exported 2D images include the lines whenever they are showing.

Extrapolated area. The 2D view outlines the borings’ footprint, the outline joining the outermost borings, and hatches the colored area past it. Inside the footprint every estimate has borings on more than one side. In the hatched, extrapolated area the estimate reaches past the outermost borings, so treat it as less certain. The volume chart can show the volume between the borings, in the extrapolated area, or both (see volume estimation), and the readme’s volume tables list all three. Untick Extrapolated area to hide the hatching and the outline; exported 2D images and the GeoTIFF never include them.

To use the lines in GIS, choose Contour Lines (GeoJSON) from the results page's Export menu. Each line comes with its %RE level (the level_pct_re property), in WGS84 longitude/latitude (EPSG:4326, which the GeoJSON standard requires and any GIS reprojects automatically), and every level is included, the same lines the 2D view draws. Each piece's extrapolated property is true where the 2D view draws it dashed. Not available on trial accounts. Borings’ Footprint (GeoJSON), on the same menu, is the footprint as one polygon, also in WGS84, so you can show or clip by it in your own map.

Plan View (GeoTIFF) on the same menu exports the 2D view as a colored image (red, green, blue and transparency, not %RE numbers), drawn with the color scheme, threshold and 2D gamma showing when you export, at 0.5 m per pixel (coarser on a site more than 1 km across), in the coordinate system named in your coordinates file. It lines up with your other GIS layers as long as that is the system your coordinates were surveyed in. Contour lines and boring markers are not part of the GeoTIFF. The settings it was drawn with (color scheme, threshold, gamma and the %RE at the top of the color scale) are stored in the file's metadata as LIFVIZ_* tags, with a note that the colors are estimates, rather than printed on the image: QGIS shows them under Layer Properties › Metadata, ArcGIS Pro in the raster’s properties.

3D (Isosurface) tab

The 3D (Isosurface) tab draws the same 3D plume as nested see-through shells at 10, 25, 50 and 100 %RE instead of a point cloud (levels the site never reaches are left out): everything above a shell's level sits inside it, and the colorbar shows one color swatch per shell. Shells below the %RE threshold slider are hidden. A shell's hard edge can look more certain than borings several meters apart really support, so read it as a guide to the plume's shape, not an exact boundary.