episode 2

carpentries-incubator · Jul 25, 2023 · e99670e · e99670e
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commit e99670e
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diff --git a/episodes/02-intro-vector-data.md b/episodes/02-intro-vector-data.md
@@ -2,16 +2,17 @@
 title: "Introduction to Vector Data"
 teaching: 10
 exercises: 5
-questions:
-- "What are the main attributes of vector data?"
-objectives:
-- "Describe the strengths and weaknesses of storing data in vector format."
-- "Describe the three types of vectors and identify types of data that would be stored in each."
-keypoints:
-- "Vector data structures represent specific features on the Earth's surface along with attributes of those features."
-- "Vector objects are either points, lines, or polygons."
 ---
 
+:::questions
+- What are the main attributes of vector data?
+:::
+
+:::objectives
+- Describe the strengths and weaknesses of storing data in vector format.
+- Describe the three types of vectors and identify types of data that would be stored in each.
+:::
+
 ## About Vector Data
 
 Vector data structures represent specific features on the Earth's surface, and
@@ -20,10 +21,7 @@ locations (x, y values) known as vertices that define the shape of the spatial
 object. The organization of the vertices determines the type of vector that we
 are working with: point, line or polygon.
 
-![Types of vector objects](../fig/E02-01-pnt_line_poly.png)
-
-Image Source: National Ecological Observatory Network (NEON)
-{: .text-center}
+![Types of vector objects (Image Source: National Ecological Observatory Network (NEON))](../fig/E02-01-pnt_line_poly.png)
 
 * **Points:** Each point is defined by a single x, y coordinate. There can be
 many points in a vector point file. Examples of point data include: sampling
@@ -38,36 +36,40 @@ vertex that has a defined x, y location.
 closed. The outlines of survey plot boundaries, lakes, oceans, and states or
 countries are often represented by polygons.
 
-> ## Data Tip
->
-> Sometimes, boundary layers such as states and countries, are stored as lines
->  rather than polygons. However, these boundaries, when represented as a line,
->  will not create a closed object with a defined area that can be filled.
-{: .callout}
-
-> ## Identify Vector Types
-> 
-> The plot below includes examples of two of the three types of vector
-> objects. Use the definitions above to identify which features
-> are represented by which vector type.
-> 
-> ![Vector Type Examples](../fig/E02-02-vector_types_examples.png)
-> 
-> > ## Solution
-> > State boundaries are polygons. The Fisher Tower location is
-> > a point. There are no line features shown. 
-> {: .solution}
-{: .challenge}
-
-Vector data has some important advantages:  
-  * The geometry itself contains information about what the dataset creator thought was important  
-  * The geometry structures hold information in themselves - why choose point over polygon, for instance?  
-  * Each geometry feature can carry multiple attributes instead of just one, e.g. a database of cities can have attributes for name, country, population, etc  
-  * Data storage can be very efficient compared to rasters  
-
+:::callout
+## Data Tip
+
+Sometimes, boundary layers such as states and countries, are stored as lines
+rather than polygons. However, these boundaries, when represented as a line,
+will not create a closed object with a defined area that can be filled.
+:::
+
+:::challenge
+## Identify Vector Types
+
+The plot below includes examples of two of the three types of vector
+objects. Use the definitions above to identify which features
+are represented by which vector type.
+
+![Vector Type Examples](../fig/E02-02-vector_types_examples.png)
+
+::::solution
+## Solution
+
+State boundaries are polygons. The Fisher Tower location is
+a point. There are no line features shown.
+::::
+:::
+
+Vector data has some important advantages:
+  * The geometry itself contains information about what the dataset creator thought was important
+  * The geometry structures hold information in themselves - why choose point over polygon, for instance?
+  * Each geometry feature can carry multiple attributes instead of just one, e.g. a database of cities can have attributes for name, country, population, etc
+  * Data storage can be very efficient compared to rasters
+
 The downsides of vector data include:
-  * Potential loss of detail compared to raster  
-  * Potential bias in datasets - what didn't get recorded?  
+  * Potential loss of detail compared to raster
+  * Potential bias in datasets - what didn't get recorded?
   * Calculations involving multiple vector layers need to do math on the
     geometry as well as the attributes, so can be slow compared to raster math.
 
@@ -82,13 +84,13 @@ their features to real-world locations.
 
 Like raster data, vector data can also come in many different formats. For this
 workshop, we will use the Shapefile format. A Shapefile format consists of multiple
-files in the same directory, of which `.shp`, `.shx`, and `.dbf` files are mandatory. Other non-mandatory but very important files are `.prj` and `shp.xml` files. 
+files in the same directory, of which `.shp`, `.shx`, and `.dbf` files are mandatory. Other non-mandatory but very important files are `.prj` and `shp.xml` files.
 
-- The `.shp` file stores the feature geometry itself 
+- The `.shp` file stores the feature geometry itself
 - `.shx` is a positional index of the feature geometry to allow quickly searching forwards and backwards the geographic coordinates of each vertex in the vector
-- `.dbf` contains the tabular attributes for each shape. 
+- `.dbf` contains the tabular attributes for each shape.
 - `.prj` file indicates the Coordinate reference system (CRS)
-- `.shp.xml` contains the Shapefile metadata. 
+- `.shp.xml` contains the Shapefile metadata.
 
 Together, the Shapefile includes the following information:
 
@@ -105,26 +107,31 @@ individual shapefile can only contain one vector type (all points, all lines
 or all polygons). You will not find a mixture of point, line and polygon
 objects in a single shapefile.
 
-> ## More Resources on Shapefiles
->
-> More about shapefiles can be found on
-> [Wikipedia.](https://en.wikipedia.org/wiki/Shapefile) Shapefiles are often publicly 
-> available from government services, such as [this page from the US Census Bureau][us-cb] or
-> [this one from Australia's Data.gov.au website](https://data.gov.au/data/dataset?res_format=SHP).
-{: .callout}
-
-> ## Why not both?
->
-> Very few formats can contain both raster and vector data - in fact, most are
-> even more restrictive than that. Vector datasets are usually locked to one
-> geometry type, e.g. points only. Raster datasets can usually only encode one
-> data type, for example you can't have a multiband GeoTIFF where one layer is
-> integer data and another is floating-point. There are sound reasons for this -
-> format standards are easier to define and maintain, and so is metadata. The
-> effects of particular data manipulations are more predictable if you are
-> confident that all of your input data has the same characteristics.
-{: .callout}
+:::callout
+## More Resources on Shapefiles
+
+More about shapefiles can be found on
+[Wikipedia.](https://en.wikipedia.org/wiki/Shapefile) Shapefiles are often publicly
+available from government services, such as [this page from the US Census Bureau][us-cb] or
+[this one from Australia's Data.gov.au website](https://data.gov.au/data/dataset?res_format=SHP).
+:::
+
+:::callout
+## Why not both?
+
+Very few formats can contain both raster and vector data - in fact, most are
+even more restrictive than that. Vector datasets are usually locked to one
+geometry type, e.g. points only. Raster datasets can usually only encode one
+data type, for example you can't have a multiband GeoTIFF where one layer is
+integer data and another is floating-point. There are sound reasons for this -
+format standards are easier to define and maintain, and so is metadata. The
+effects of particular data manipulations are more predictable if you are
+confident that all of your input data has the same characteristics.
+:::
 
 [us-cb]: https://www.census.gov/geographies/mapping-files/time-series/geo/carto-boundary-file.html
 
-{% include links.md %}
+:::keypoints
+- Vector data structures represent specific features on the Earth's surface along with attributes of those features.
+- Vector objects are either points, lines, or polygons.
+:::