How to Save as in 1 GeoTIFF file the hillshade raster and colored raster layer in QGIS 3.4.4?

Level Up Your Maps: Combining Hillshade and Color in QGIS (the Easy Way!)

Alright, map geeks and GIS wizards, let’s talk about making seriously stunning maps in QGIS. You know how a hillshade can make your terrain pop, giving it that awesome 3D look? And how a colored raster – maybe a satellite image or a land cover map – brings in the details? What if you could combine them and save it all as a single, neat GeoTIFF file? Sounds good, right? It’s totally doable, and I’m going to walk you through it in QGIS 3.4.4.

Now, you might be thinking, “Why bother? Why not just keep them separate?” Well, think about it: one file is easier to manage, share, and play nice with other software. Trust me, your future self will thank you.

The trick is, a GeoTIFF usually holds just one raster layer. So, we need to get a little creative. We’ve got two main approaches here, depending on what you’re trying to achieve.

Option 1: The Analytical Powerhouse (Multi-band Raster)

This is the way to go if you’re not just making pretty pictures. If you need to actually use the data from both the hillshade and the colored raster for analysis later on, this is your jam. We’re talking about creating a single GeoTIFF where the hillshade lives in one “band” and the colored raster gets the other bands (usually three for those vibrant RGB colors).

• First things first: Fire up QGIS and make sure you’ve got both your hillshade and your colored raster loaded and ready to roll.

• Step 1: Get on the Same Page (Reproject, if Needed): This is super important. Make sure both rasters are using the exact same Coordinate Reference System (CRS). Think of it like speaking the same language. If they’re not, QGIS has a handy “Warp (Reproject)” tool (look under Raster -> Projections) that’ll translate one to match the other. Don’t skip this!

• Step 2: Size Matters (Align Those Rasters!): Next up, make sure your rasters are the same size and have the same cell size. Again, the “Warp (Reproject)” tool is your friend. You’ll want to resample one to match the other. I usually resample the hillshade to match the colored raster, just to keep the original color data as crisp as possible.

• Step 3: Merge Mania: Okay, time to bring them together! Head over to Raster -> Miscellaneous -> Merge. A window will pop up, asking for input layers. Click that button and select both your hillshade and your colored raster. Pay attention to the order you select them – the first one becomes the first band. Now, check that box that says “Place each input file into a separate band.” Give your new file a name (ending in “.tif,” of course), pick a data type (usually “Byte” is fine, but go bigger if your data needs it), and hit “Run.”

• Step 4: The Grand Reveal: Load up your newly minted GeoTIFF in QGIS. You should see one layer, but it’s secretly got multiple bands inside. You can style each band separately to get the look you want. Pretty cool, huh?

Option 2: The Visual Artist (Layer Rendering and Export)

Alright, let’s say you’re all about the visuals. You want a map that looks amazing, but you don’t necessarily need to analyze the raw data later. This method is for you! We’re going to tweak the way the layers look and then export the whole shebang as a single GeoTIFF.

• Setup: As before, make sure you’ve got your hillshade and colored raster loaded in QGIS. Style that hillshade so it looks nice and shadowy – usually a grayscale palette works best.

• Step 1: Layer Cake (Order and Transparency): In your “Layers” panel, make sure the colored raster is on top of the hillshade. Now, the magic happens: adjust the transparency of the colored raster. Right-click on it, go to “Properties,” and then “Transparency.” Play with that “Global transparency” slider until you can see the hillshade peeking through. You can even set different transparency levels for different data ranges for extra control.

• Step 2: Get Creative (Blending Modes – Optional!): This is where you can really get artistic. In the “Layer Properties” for the colored raster, check out the “Blending” tab. Experiment with modes like “Multiply” or “Overlay.” These can create some seriously cool effects when combining the layers. It’s like Instagram filters for your map!

• Step 3: Export Time: Ready to save your masterpiece? Go to Project -> Import/Export -> Export Map to Image. A dialog box will appear. Give your file a name (ending in “.tif,” naturally). Set the width and height for the resolution you want. Crucially, make sure the “World File” option is checked. This creates a little “.tfw” file that tells other GIS programs where your image is located in the world. In the “Map extent” section, select the area you want to export. Hit “Save,” and you’re done!

• Step 4: Double-Check (Georeferencing, if Needed): Sometimes, even with the “World File,” your exported image might not line up perfectly. If that happens, you’ll need to manually “georeference” it using the Georeferencer tool (Raster -> Georeferencer). It sounds scary, but it’s just a matter of picking points on your image and matching them to real-world coordinates. But if you checked that “World File” box, you should be good to go!

Pro Tips and Things to Keep in Mind

• Data Types Matter: Think about the kind of data you’re working with when you choose a data type for your output GeoTIFF. Smaller data types save space, but you might lose some detail.
• Compression is Your Friend: Use compression (like LZW or DEFLATE) to keep those file sizes down.
• CRS, CRS, CRS! I can’t stress this enough: make sure everything is in the same Coordinate Reference System.
• Resolution vs. File Size: Higher resolution maps look great, but they also take up more space. Find the sweet spot for your needs.
• QGIS Versions: I’m talking about 3.4.4 here, but most of this applies to other versions too. Just poke around the menus a bit if things look different.

Wrapping Up

So there you have it! Combining hillshades and colored rasters in QGIS isn’t rocket science, but it can seriously boost the visual impact of your maps. Whether you’re crunching data or just making something beautiful, these techniques will help you take your GIS skills to the next level. Now get out there and make some maps that wow!