Fix for non-mercator tiles (CrunchyData#61)

layer_table.go

@@ -331,6 +331,7 @@ func (lyr *LayerTable) requestSql(tile *Tile, qp *queryParameters) (string, erro
  type sqlParameters struct {
  TileSql string
  QuerySql string
+ TileSrid int
  Resolution int
  Buffer int
  Properties string
@@ -350,6 +351,10 @@ func (lyr *LayerTable) requestSql(tile *Tile, qp *queryParameters) (string, erro
  tileSql := tileBounds.SQL()
  tileQuerySql := queryBounds.SQL()
 
+ // SRID of the tile we are going to generate, which might be different
+ // from the layer SRID in the database
+ tileSrid := tile.Bounds.SRID
+
  // preserve case and special characters in column names
  // of SQL query by double quoting names
  attrNames := make([]string, 0, len(qp.Properties))
@@ -371,6 +376,7 @@ func (lyr *LayerTable) requestSql(tile *Tile, qp *queryParameters) (string, erro
  sp := sqlParameters{
  TileSql: tileSql,
  QuerySql: tileQuerySql,
+ TileSrid: tileSrid,
  Resolution: qp.Resolution,
  Buffer: qp.Buffer,
  Properties: strings.Join(attrNames, ", "),
@@ -390,7 +396,7 @@ func (lyr *LayerTable) requestSql(tile *Tile, qp *queryParameters) (string, erro
  tmplSql := `
  SELECT ST_AsMVT(mvtgeom, {{ .MvtParams }}) FROM (
  SELECT ST_AsMVTGeom(
- ST_Transform(ST_Force2D(t."{{ .GeometryColumn }}"), 3857),
+ ST_Transform(ST_Force2D(t."{{ .GeometryColumn }}"), {{ .TileSrid }}),
  bounds.geom_clip,
  {{ .Resolution }},
  {{ .Buffer }}