A simple visibility simulation

Now in component placement/sizing mode

Upload uvpoints file:
Note: file format should be ASCII text, with columns u, v, and time.

Comp. index Xpos Ypos Xsigma Ysigma Brightness PA
1 0. 0. 50. 50. 1. 0.
2 0. 0. 50. 50. 0. 0.
3 0. 0. 50. 50. 0. 0.
4 0. 0. 50. 50. 0. 0.
5 0. 0. 50. 50. 0. 0.
6 0. 0. 50. 50. 0. 0.
7 0. 0. 50. 50. 0. 0.
8 0. 0. 50. 50. 0. 0.
9 0. 0. 50. 50. 0. 0.
10 0. 0. 50. 50. 0. 0.


Point index U coord V coord Time Amp Phase
1 0. 0. 0.

Above, we show an interactive canvas with a sky image of some hypothetical radio source on the left, consisting of up to 10 separate source components. On the right, the colourful area shows the interferometric visibility map that corresponds to the sky image on the left. Source image components can be added, edited or removed to see what effect they have on the visibility map. If you're starting out, try to move the single source component around by using the arrow keys, and see how the phases of the visibilities get affected.

Everything can be controlled using the keyboard (see controls at the bottom of the page), but there is also an elementary mouse interface. Left-clicking anywhere in the left subplot will place the active source component at that location. Left-click and drag allows you to adjust the size of the active source component. Right-clicking or dragging anywhere will adjust the major axis of the active source component. There are 4 modes for the keyboard interface, and you can switch between them by pressing 'j'. The controls that are valid for each mode, visible at the bottom of this page, are updated whenever you switch modes.

Note that this is a very early version: many of the functions that I mean to add have not been implemented yet. If you have questions, comments or suggestions for improvements and/or functional extension, I will be happy to hear from you. Please contact me at my department email address (c dot brinkerink at astro dot ru dot nl).

For a list of all controls, see bottom of page.

Controls for currently active mode

single-press actions

[ and ] keys: cycle through all 10 components to select the active source component (the selected component is indicated by a thin green bar at the very bottom of the sky image that jumps left or right when you switch selections - look carefully). There are 10 source components in total that can all be modified. In the sky image, the active source component is coloured magenta.

q key: switch the type of the current source component between 2D Gaussian and circular disk. For the disk, only sigma-x is used to determine its size.

m key: center active component in middle of sky image.

n key: normalize strength of active component to 1.

b key: set sigma-x and sigma-y of active component to 50 pixels.

0 key: set strength of active component to zero.

u and i keys: change zoom level of sky image.

o and p keys: change zoom level of visibility map.

f,g,h keys: darken the r,g,b components of the visibility phase colour map.

r,t,y keys: brighten the r,g,b components of the visibility phase colour map.

k and l keys: change the size of the displayed window to make it fit your screen.

Press-and-hold actions

Cursor keys: move active component across sky image.

w,a,s,d keys: change sigma-x (a and d) and sigma-y (s and w) of the current component.

comma and period keys: rotate the active component on the sky, if it is a Gaussian.

z and x keys: change strength of active component. Strength can be negative so that flux can be subtracted from other elements. When sky flux density becomes negative anywhere, this is indicated with a red colour.

c and v keys: change brightness scale of sky image.

minus and equals keys: change brightness scale of visibility map.