25 March 2017

Building a Web Map, Part 2

Alright, I was finally able to get some basic markers and popups to work.  I wasn’t able to accomplish as much this week as I was hoping.  I ended up working extra hours this week because I was off school for spring break, so I couldn’t spend that time working on the map as I had planned.

Before placing any locations on the map, I organized the data I had preciously collected into one excel file. I split the locations into two broad categories, adventure locations and population locations. for adventures, I included data about type of adventure, ruin, dungeon, lair, mine, and graveyard; type of monsters present such as humanoid, or undead; the big boss of the adventure; and the source where the adventure can be found. For population centers I included different categories, type of population center, total population, faction loyalty, military capability, the current ruler, and main economic activities. For this category I included major humanoid locations that were the locations of a lair for an entire tribe.

Once I had all this data organized, I needed to create actual points in ArcMap to match to all the locations. To do this I used Thorfinn Tait’s updated map of Karameikos modified with forested hills as a reference. I was able to georeference this 8mph using the24mph expert map as a basis. however, this map doesn’t match up perfectly and I had to use more than two control points to get it to line up, even then it still doesn’t completely agree with the earlier 6mph map or the 24 mph map published in the expert set. The most notable differences occur in the route of the rivers and the shape of the peninsula by Specularum. There are also more hexes classified as mountainous as opposed to hilly, and some of the settlements are off by a smidge. These differences can be seen in the image below, the 8mph map is displayed at 50%transparency on top of the other maps with the created locations symbolized as red and purple circles. Once I had this reference map in place, I was able to create a new shapefile and add points features to it for each location. I used the 6mph map as a primary source, and where a location wasn’t marked on that map, I used the 8ph map.

With the point locations created, now I needed to join the data from my excel file to the shapefile. this proved troublesome. the join tool failed to operate when I attempted to join the two attribute tables with the excel table. I could have figured out the issue, which probably had something to do with the formatting of the excel table, but since I hadn’t created a great number of points I decided to just copy and paste the data from the excel file to the attribute table of the shapefile.

With my work in ArcMap completed, I moved on to moving the features I had created into the web map. This is where the most time was spent and I kept running into roadblocks. The main goal here was to convert the shapefile into a geoJSON format and then use that to create popups displaying the properties of each marker.  Converting to geoJSON seemed to be easy at first. There was a tool in ArcMap which allowed me to easily do this. however, the end result had to be modified. This is what the tool gave me for the adventure site of Koriszegy Keep:

{"type":"FeatureCollection","crs":{"type":"name","properties":{"name":"EPSG:3857"}},"features":[{"type":"Feature","id":0,"geometry":{"type":"Point","coordinates": 419432.17583047762,3141498.3623768883]},"properties":{"FID":0,"Id":0,"Name":"Koriszegy Keep","Type":"Ruins","Monsters":" Humanoids, Werewolves, Undead, Lowlife","Boss":" Rodemus Family","Module":"Modlvay Basic"}}]}

The issue here is the coordinates provided. In order for the point to be displayed properly the x and y values must be in decimal degrees; currently a northing and easting are displayed in meters, specific to the projection used (web Mercator). Also, the latitude and longitude values need to be swapped, so they appear as long(x), lat(y). Also, seen in the code above is the definition of the projection used (the section following crs), this can be deleted as the coordinates used in the future will be unprojected in decimal degrees. The resulting geoJSON feature looks like this:

{"type" : "FeatureCollection",  "features" : [{"type" : "Feature", "id" : 0, "geometry" : { "type" : "Point", "coordinates" : [3.76782, 27.1442 ]}, "properties" : {"FID" : 0,"Id" : 0,"Name" : "Koriszegy Keep", "Type" : "Ruins", "Monsters" : " Humanoids, Werewolves, Undead, Lowlife", "Boss" : " Rodemus Family", "Module" : "Modlvay Basic"} } ] }

When first trying to import this geoJSON into leaflet, nothing would happen. the feature was inserted as a variable within the body of the script at first, with the L.geoJson following the map initialization. I tried several different things to get it to work, some of which caused the map to not even initialize. I even attempted to use mapbox to display the data. I was able to upload the data, and display points, but o make popups work I had to rewrite the entire map code from scratch in the mapbox GL JS. This I failed to execute successfully, so I gave up on that. After a day of not being able to get anything done I was able to find some more examples and resources about geoJSON that I had not looked at before. I ended up placing the geoJSON variables in the header of the document in two separate scripts for each variable. It may not have been the most efficient way to write it, but it ended up working.  The last part I did was to have the markers be clickable and display the properties of each feature. This was done using the onEachFeature function combined with layer.bindPopup.

This post has grown larger than I expected, given the changes made to the map are relatively minor. In the next few weeks I will be adding more markers, different symbols based on feature type, a base map of my own devising, and possibly a routing option. If you have any comments about the process far, or have input about how the data should be displayed please leave a comment.