Example: Transform Template Units

Templates in  the Transform panel often include parameter boxes using units of measure.  This example uses the Buffer drawing template to show how to change units of measure quickly to whatever units are desired.


We open a map as seen below.   The map is in default Pseudo-Mercator projection.  It contains two layers: a background layer showing satellite photography from Bing and a Dot drawing layer that contains a dot.  Both layers are also in Pseudo-Mercator, the projection used by Bing and most other web servers.  


In front of the Capitoline Museum we see the plaza designed by Michelango in 1538, with an exact copy of the Roman bronze equestrian statue of the Emperor Marcus Aurelius in the center.




The green dot marks the spot where we intend to fly a small drone with a camera, to take close up photos of the statue.  We can get away with using a drone in the plaza, but not inside the museum where the original is on display.   


We purchased the drone in a budget electronics store in Kowloon: it is intended for indoor use and the instructions say we can control it with our smart phone using Bluetooth up to a distance of 30 something units.  The units are unclear since the printed  instructions are in Chinese.   We don't know if the 30 means 30 meters or 30 feet.   We will try different buffer sizes to see what "30" might imply for operational radius.




We open the Transform panel and choose the Buffer template.  In the Distance parameter box we enter 30.   The default units setting is m for meters, the units of measure used by the target Geom field in the Pseudo Mercator coordinate system the Dots drawing uses.




Right away, the system draws a preview showing the buffer size with a radius of 30 meters.   We can see that if our drone can be controlled at a distance of 30 meters from where we will stand we will have no problem flying it about the statue.  But what if the "30" in our drone's user manual means 30 feet?




To change the unit we click on the m unit.




In the resulting menu we choose the Unit submenu.




In the incredibly long list of units that appears, we choose Foot.





That sets the Distance parameter box to using feet as a unit of measure, indicated by ft.  The buffer radius will now be computed as 30 feet.




Instantly, the preview alters to show what a buffer of radius 30 feet would be.   Clearly, if the user manual for our drone means it can only be controlled up to 30 feet by Bluetooth, we must make sure to stand closer to the statue.




At any time we can tell the system to use whatever are the native units of the coordinate system.   We simply choose Native in the Units list.




Use of native units is indicated with a u.   This is the abbreviation used in cases such as images where the size of pixels in X and Y direction might be different.




In this case, the native units are meters, so the buffer preview is the same as for meters.




If we forget what native units are used by a component we can always switch the Contents pane to the Components panel to see.   If we switch back to the Transform panel and choose the Buffer transform again, the Distance box will go back to using m for meters as the default.


See Also



Contents - Transform


Example: How Images use Tiles from Tables - An example showing how an image is made up from data stored in a table in tiles.


Example: Create Two Images From One Table - More than one image can show data from the same table, including from the same tile field.


Example: An Image using Computed Fields in a Table - How an image can be created from tiles where the data for the tiles is taken from a field that is computed on the fly.


SQL Example: Re-tile an Image using a Different Tile Size - Starting with an image that uses a tile size of 128 x 128 pixels this SQL example creates a copy of the image using 500 x 500 pixel tiles.


SQL Example: Kriging - We use SQL functions to create a raster terrain elevation image from vector contour lines in a drawing, using SQL functions for Kriging interpolation.


Example: Merge Images - A step-by-step example using the Merge Images command showing how to merge dozens of images showing SRTM terrain elevation data into one image, with various tricks for faster workflow as an experienced Manifold user would do the job.  After creating the new image we style it with a palette and use hill shading to better show terrain elevation.


Example: Contour Areas and Contour Lines - In this example we use the Contour Areas transform template in the Transform panel for images to create a drawing with vector areas showing height contours at desired altitude steps.   We color the areas using the attribute fields automatically created by the template.  Next, we apply a similar procedure using the Contour Lines transform template to create a drawing with vector lines showing height contours at the desired intervals.