diff --git a/contours/Makefile b/contours/Makefile
index 6530379..3efc5de 100644
--- a/contours/Makefile
+++ b/contours/Makefile
@@ -39,8 +39,7 @@ all.xyz: $(XYZ)
 .INTERMEDIATE: $(XYZ)
 %.xyz: %.zip
 	unzip -qq -c $< $@ | \
-		sed -e 's/^ \+//' -e 's/ \+/,/g' | \
-		./clip.awk $(addprefix -v ,$(BOUNDS)) | \
+		./clip-2009.awk $(addprefix -v ,$(BOUNDS)) | \
 		$(SORT) > $@
 
 db/.ready: managedb
diff --git a/contours/clip-2009.awk b/contours/clip-2009.awk
new file mode 100755
index 0000000..0b02549
--- /dev/null
+++ b/contours/clip-2009.awk
@@ -0,0 +1,7 @@
+#!/usr/bin/awk -f
+
+# this file works with SEZP from circa 2009, where x coordinate (the 6-digit one)
+# is first, and the field separator is ' ' or more spaces.
+$1 > xmin && $1 < xmax && $2 > ymin && $2 < ymax {
+    print $1 "," $2 "," $3
+}
diff --git a/contours/clip.awk b/contours/clip-2017.awk
similarity index 50%
rename from contours/clip.awk
rename to contours/clip-2017.awk
index 3d677b0..5ed6b6f 100755
--- a/contours/clip.awk
+++ b/contours/clip-2017.awk
@@ -1,4 +1,7 @@
 #!/usr/bin/awk -f
+#
+# this file works with SEZP circa ~2017 where y coordinate (the 7-digit one) is
+# first, and the field separator is ','
 BEGIN {
     FS = ","
 }