China’s data used to be surprisingly easy to get hold of, but sadly they have changed their website into what on the asurface is a more user friendly format, but actually is less easy to fathom out what you need.
There are two probes from which to get data, Chang’e-
CE1’s files are much smaller and have a lower resolution, but they are useful ones to have as a way of checking which file you need to look at in the more detailed dataset.
The data for each sections consists of a .lbl, a .tfw and a ‘.03’ file. The lbl files can be used in GIS software, but are not always required. The tfw file is one that contains simple information about a photograph’s location. The .03 file can be used in the same software that opens the CE2 data. For most things, the TIF image is just fine here and it can be opened in any image viewing software.
First, go to the link above and register on the site. I’ve not had any issues resulting from this. Next, click on ‘Scientific Data’.
What isn’t immediately obvious is that the images are divided into 3 parts, and so far you’ve only opened on of them. If you were sure you’d captured the right part of the image you could just save it now, but if you do that it seems to stop it from letting you open the other parts of the picture. So, my recommended procedure is to go straight to the ‘Large Image Selection’ menu and go to the ‘Next Line Samples’. Do this twice and you’ll have all three elements of the image open.
All you need to do now is to save these sub-
If you have a GIS package like QGIS (discussed on the JAXA page here), you can load the .03 file in there by dragging it into the layers panel.
This allows you to browse over the whole image, and also to export it as an image file in the format of your choice.
QGIS allows the export of just the area shown in the frame, so you can zoom in and get a more detailed image export.
At the time of writing the individual tiles for China’s elevation model aren’t available, but after I emailed them they sent me a temporary link to the global DEM -
The only slight snag is the projection of the map -
So, how does this work? The first step is, as usual, to load the DEM and photographic layers into your GIS package, and as with other probe data I‘ll be using QGIS. Here’s the view with the DEM and the CE2 tile covering Hadley Rille loaded.
It’s difficult to tell, but the actual location of the photographic tile should be some distance north-
Next, click on the left-
Hopefully you can see above the role the different map projections play in things -
The easiest features to look for are craters, as they stand out on both maps, whereas a change in elevation marking a bright mountain feature could be too subtle to identify accurately. Georeferencing in QGIS needs a minimum of four co-
The next step is to tell the Georeferencer that you want to add a point, which is done by clicking the ‘add point’ icon:
The other two icons there are ‘Delete point’ if you get one wrong (just click that icon then click on the point you want to get rid of), and then ‘Move point’ if you get one in the wrong place. My method here is to click on the exact centre of the crater I want to use as a reference. In the image below I’ve zoomed right in on a crater I’ve identified as being in both layers. Clicking first in the georeferencer window you’ll get another box pop up asking for coordinates of the point on the main map. If you actually know them then great, by all means type them in but it’s much easier just to click on the ‘From map canvas’ button and click on the equivalent point in the main GIS window. Note you can move from window to window and zoom in and out using the scroll wheel on your mouse.
As you move onto the main window, the From map coordinates box will disappear, and it will reappear once you’ve clicked on it with the coordinates of the point you’ve added filled in in both the box and below the georeferencer window. I should point out that to save space the image above is a composite showing all parts of the process -
Repeat this process as many times as you can to get the most accurate transformation.
Once you’ve got your minimum of four points, you need to click on the ‘cog’ icon to tell it how you want to do the georeferencing. You’ll get the following:
Again this is a composite window showing everything you need. By default the ‘Create world file’ tick box may be selected -
You also need to choose the ‘Target SRS’ to match the one on the map. If you forget this you can still select it in the main program when you’re done.
Click on OK when you’re happy. The final step is to click the big green triangle ‘Start Georeferencing’ icon.
You’ll see a couple of windows appear telling you it’s working, then some ‘OK’ buttons to click when it’s done. With any luck if you selected your referencing points accurately you should see an accurately plotted photographic layer appear. When you close the Georeferencer you’ll see messages about keeping or discarding the reference points you added -
What you can also do is try and generate a 3D view using the Chinese data -
It should be obvious what the different resolution has done to the detail in the map -
If you want to have a go at the Apollo sites yourself, I have uploaded the Global DEM and CE1 and CE2 files to a Dropbox account. The links are given below. The values in brackets are the map subdivisions on China’s map if they ever come up again:
Have fun exploring China’s space data!
It will now read the file and open it as it would any other image. Job done, and you can play around to your heart’s content!
This method will work for CE1 and CE2 .03 files.
If you don’t have Photoshop, you’ll need to use NASAView. Go to the file menu and select ‘Open Object’. Browse to the directory containing the file and select it. You’ll see a window like this:
You’ll get a dialogue box with image details in. You can just accept what it comes up with and hit ‘OK’.
To get the highest quality data, click the ‘CE2’ link, and choose the 03-
You’ll get a lot of pages of results -
If you look at the file name, you’ll see after the ‘CE2_BMYK_CCD_DIM’ part is a letter and number, eg K003, J018. These refer to the sections of the map image I posted at the top of this page.
Once you have the files you need you’ll want to do something with them. Photoshop users have a simple way of opening the .03 files using built in features. This document describes the process for files in ‘.IMG’ format from the Lunar Reconnaissance Orbiter, but it also works for China’s .03 format.
First, instead of going to ‘File’, ‘Open’, go to ‘File’, ‘Open As’. From the ‘Open As’ list choose ‘Photoshop RAW’.