NetCDF in ArcMap Class 04:  Georeferencing Image file using Co-ordinates скачать в хорошем качестве

NetCDF in ArcMap Class 04:  Georeferencing Image file using Co-ordinates

Mastering Georeferencing in ArcMap: A Step-by-Step Guide for Guatemala 🗺️💾 This session focuses on georeferencing an image of Guatemala within ArcMap, covering two essential methods. This process is vital for accurately aligning spatial data for analysis and comparison. Method 1: Georeferencing Using a Reference Map (World Administrative Boundaries) Preparation: First, extract the provided "georeferencing" zip file. This contains the Guatemala image and an associated ArcMap file. Open a new ArcMap project and add the Guatemala image to your map. Initial Setup: The Guatemala image is initially unprojected. To address this, use the "Define Projection" tool found in ArcMap's search bar. Select the Guatemala layer and choose the "Geographic Coordinate System" - "World" - "WGS 1984" coordinate system. This step establishes a standard geographic reference for your image. Establishing Control Points: Zoom in on the Guatemala image to clearly identify the intersections of grid lines, which represent longitude and latitude. Activate the "Add Control Points" tool. Important Note: When locating points on the western side of the map (like Guatemala), ensure you use negative values for longitude (e.g., -92, -89). Latitude values will remain positive. Click on an intersection point on the Guatemala image. Then, right-click and input the corresponding X (longitude) and Y (latitude) coordinates. Repeat this for a minimum of four points. It's best to select points that are easily identifiable on both the Guatemala image and a reference map, such as the world administrative boundaries shapefile. Saving the Georeferenced Layer: After setting your control points, navigate to the "Georeferencing" toolbar and select the "Rectify" option. Save the rectified image as a new file (preferably a GeoTIFF) in a dedicated folder for your project. Method 2: Extracting a Specific Area (Guatemala) using Select by Attributes and Extract by Mask Preparation: Ensure you have the rectified Guatemala TIFF file from Method 1 and the world administrative boundaries shapefile ready. Selecting Guatemala with Attributes: Open the attribute table associated with the world administrative boundaries shapefile. Utilize the "Select by Attributes" tool. Construct a query: For example, French = 'Guatemala' (adjust the field name and value if necessary based on the data). Apply this query to highlight Guatemala on your map. Extracting the Guatemala Area: In ArcMap's search bar, locate the "Extract by Mask" tool. For the "Input Raster," select your rectified Guatemala TIFF file. For the "Input Raster or Feature Mask," choose the Guatemala polygon feature from the world administrative boundaries shapefile. Specify the output folder and a filename for your extracted Guatemala map. Execute the tool to create a new raster containing only the Guatemala area.| Key Concepts: Georeferencing: The process of spatially aligning data with a known geographic coordinate system. Projection: Converting data from one coordinate system to another. Control Points: Matching identifiable points on your source data to their corresponding locations on a reference map. Rectify: A georeferencing method that creates a new, georeferenced raster file. Extract by Mask: A tool used to clip a raster dataset to the boundaries of a feature (like a country or study area). Practice Exercise: Try georeferencing your own country or a specific study area using the world administrative boundaries and the techniques demonstrated. This skill is essential for upcoming exercises involving data analysis across various regions. #Georeferencing #ArcGIS #ArcMap #Guatemala #GIS #SpatialData #RasterData #Shapefile #ExtractByMask #CoordinateSystem #GeoSpatialAnalysiss