Add some examples to the SqDist usage readme.

docs/algorithms/SqDist.md

 Geomagnetic Secular Variation, Solar Quiet, and Disturbance
-=====================================
+===========================================================
 
 E. Joshua Rigler <[erigler@usgs.gov](mailto:erigler@usgs.gov)>
 

docs/algorithms/SqDist_usage.md

@@ -6,6 +6,48 @@ The Solar Quiet and Disturbance Algorithm calculates `Solar Variation`,
 
 `geomag.py --algorithm sqdist`
 
+
+### Example
+
+This example uses a state file to produce magnetic-h-based Dist, SQ, and SV
+channels using the EDGE channel naming convention.
+
+    bin/geomag.py \
+      --input-edge cwbpub.cr.usgs.gov \
+      --observatory BOU \
+      --inchannels H E Z F \
+      --starttime 2016-01-03T00:01:00 \
+      --endtime 2016-01-04T00:00:00 \
+      --algorithm sqdist \
+      --sqdist-mag \
+      --sqdist-statefile=/tmp/sqdist_h_state.json \
+      --rename-output-channel H_SQ MSQ \
+      --rename-output-channel H_SV MSV \
+      --rename-output-channel H_Dist MDT \
+      --outchannels MDT MSQ MSV \
+      --output-iaga-stdout
+
+This example processes just one channel (X).
+
+    bin/geomag.py \
+      --input-edge cwbpub.cr.usgs.gov \
+      --observatory BOU \
+      --inchannels X \
+      --starttime 2016-01-03T00:01:00 \
+      --endtime 2016-01-04T00:00:00 \
+      --algorithm sqdist \
+      --sqdist-statefile=/tmp/sqdist_x_state.json \
+      --rename-output-channel X_Dist MXT \
+      --rename-output-channel X_SQ MXQ \
+      --rename-output-channel X_SV MXV \
+      --outchannels MXT MXQ MXV \
+      --output-iaga-stdout
+
+> Note only one inchannel is specified and the --sqdist-mag option is omitted.
+
+
+### Library Notes
+
 > Note: this library internally represents data gaps as NaN, and factories
 > convert to this where possible.