Drupal in aerospace - selling geodetic satellite data with Commerce - Martin Mayer

A Game Changer for the Geospatial Data Market
Dauria Aerospace
develops new ways in
building low cost
satellites, thus reducing
costs for earth
observation data
drastically.
Martin Mayer, Diplom Systems Practitioner (Open) info@socialoom.org

The Game Changer for the Geospatial Data Market
Affordable Geo data allow
small businesses to pioneer
new business models.
Example:
Low cost parcel monitoring
service for local farmers

Building Satellites with Smartphone Technology

Building Lightweight Satellites
Conventional Satellite
New Satellite

Less Expensive Launches

We need a Configurable Product with a Map

Commerce's Standard Handling of Product Variations
http://demo.commerceguys.com/ck/tops/guy-short-sleeve-tee

The Customizable Products Module
As the ancient
Drupal Proverb goes:
There's a module
for that

Configuration of References
Content Type for the
Product Display
Configuration:
Add Product Reference
Set „Product Types that
can be referenced“
to Product Type;
Set „Add to Cart Line
Item Type“
to Line Item Type
Product Display Node
Configuration:
Set „Product Reference“
to Product
Product Type
Configuration:
Set „Default Reference“
to Content Type
Product
Configuration:
Set „Referenced by“
to Product
Display Node
Line Item Type
Configuration:
Set „Add to Cart Line
Item Type“
to itself (self reference!)

Validating User Inputs

Utilizing PostGIS
PostGIS extends PostgreSQL Databases with geodetic functions

The PostGIS Module integrates this Functions into Drupal
class PostgisGeometry {
...
function validate() {
$geo = is_null($this->wkt) ? $this->geometry : $this->wkt;
try {
$result = db_query("SELECT ST_GeometryType(:geo), ST_IsValid(:geo), ST_IsValidReason(:geo) as reason",
array(':geo' => $geo))->fetchAssoc();
// Return reason if geometry is not valid.
if (!$result['st_isvalid']) {
return array(
'error' => 'postgis_unparsable',
'message' => t('Not a valid geometry: @reason.', array('@reason' => $result['reason'])),
);
}
...
}
catch (PDOException $e) {
// TODO: catch only WKT parse errors.
return array(
'error' => 'postgis_unparsable',
'message' => t('Unable to parse WKT: ' . $geo),
);
}
}

But the PostGIS Module has some Weaknesses
/**
* Calculates diffrence to a given geometry.
*
* @param PostgisGeometry $geometry
* Geometry which this instance will be compared to.
*
* @return PostgisGeometry
* Geometry of diffrence.
*/
function diff($geometry) {
...
$geo_diff = db_query("SELECT ST_Union(ST_Difference(:geo_a, :geo_b), ST_Difference(:geo_b, :geo_a))",
array(':geo_a' => $geo_a, ':geo_b' => $geo_b))->fetchField();
$geo_type = db_query("SELECT GeometryType(:geo_diff)",
array(':geo_diff' => $geo_diff))->fetchField();
$diff = new PostgisGeometry($geo_type, $this->srid);
$diff->fromGeometry($geo_diff);
return $diff;
}
- Some important geodetic functions are not implemented
- Error handling is inconsistent

Extending and Overwriting the PostGIS Module
class PostgisGeometries extends PostgisGeometry {
...
function intersects($geometry) {
if ((get_class($geometry) !== 'postgis_geometry') && (get_class($geometry) !== 'PostgisGeometries')) {
throw new PostgisGeometryException('not postgis_geometry');
}
try {
$geo_a = $this->getText();
if(stripos($geo_a,'GEOMETRYCOLLECTION(' ) === 0) {
$geo_a = substr(strstr($geo_a, '('),1, -1);
}
$geo_b = $geometry->getText();
if(stripos($geo_b,'GEOMETRYCOLLECTION(' ) === 0) {
$geo_b = substr(strstr($geo_b, '('),1, -1);
}
$intersects = db_query("SELECT ST_Intersects(text :geo_a, text :geo_b)",
array(':geo_a' => $geo_a, ':geo_b' => $geo_b))->fetchField();
return $intersects;
}
catch (PDOException $e) {
throw new PostgisGeometryException( $e->getMessage( ) , (int)$e->getCode( ) );
}
}

Writing a module to validate the AOI and calculate the price
function water_quality_form_alter(&$form, &$form_state, $form_id) {
...
$form['line_item_fields']['field_line_item_map'][LANGUAGE_NONE][0]['wkt']['#element_validate'][] =
'water_quality_aoi_validate';
...
function water_quality_aoi_validate($element, &$form_state) {
...
$coverage_region_comparison->transform($aoi->getSrid());
$coverage_region_comparison->dump();
$intersects_google_projection = $coverage_region_comparison->intersects($aoi_comparison);
if ($intersects_google_projection){
// Convert aoi to srid of the region.
$aoi_comparison->transform($coverage_region['region']->getSrid());
$aoi_comparison->dump();
// check if the aoi intersects with the region. This needs to be
// done in the SRID of the coverage region for accuracy.
$within = $aoi_comparison->within($coverage_region['region']);
if ($within){
...
...

The Open Layers Editor has some Bugs
What it
should deliver
POLYGON((1066993.16984217 4873953.49407963,
1340943.47921804 5392502.29411237,
1810572.58092165 5382718.35450175,
1979345.539345157 5106322.0602720035,
1849708.33939679 4776114.09813913,
1066993.16984217 4873953.49407963))
GEOMETRYCOLLECTION(
POLYGON((1066993.16984217 4873953.49407963,
1340943.47921804 5392502.29411237,
1810572.58092165 5382718.35450175,
1979345.539345157 5106322.0602720035,
1849708.33939679 4776114.09813913,
1066993.16984217 4873953.49407963)),
POINT(1203968.324530105 5133227.894096),
POINT(1575758.0300698448 5387610.32430706),
POINT(1894959.0601334036 5244520.207386877),
POINT(1914526.9393709735 4941218.079205567),
POINT(1458350.75461948 4825033.79610938),
POINT(1066993.16984217 4873953.49407963),
POINT(1340943.47921804 5392502.29411237),
POINT(1810572.58092165 5382718.35450175),
POINT(1979345.539345157 5106322.0602720035),
POINT(1849708.33939679 4776114.09813913))
What it
sometimes
delivers
GEOMETRYCOLLECTION()

Caching and the
Open Layers Editor
have an awkward
relationship

$form_state['no_cache'] = TRUE;
if (isset($form_state['values']['line_item_fields']['field_line_item_map'][LANGUAGE_NONE][0]['wkt'])){
$form_state['input']['line_item_fields']['field_line_item_map'][LANGUAGE_NONE][0]['wkt'] =
$form_state['values']['line_item_fields']['field_line_item_map'][LANGUAGE_NONE][0]['wkt'];
} else {
if (isset($form_state['input']['line_item_fields']['field_line_item_map'][LANGUAGE_NONE][0]['wkt'])){
$wkt = $form_state['input']['line_item_fields']['field_line_item_map'][LANGUAGE_NONE][0]['wkt'];
if(stripos($wkt, 'POINT') !== false){
$wkt = substr(strstr($wkt, '('), 1,(stripos($wkt, ',POINT') - stripos($wkt, '(') -1));
}
$form['line_item_fields']['field_line_item_map'][LANGUAGE_NONE][0]['wkt']['#value'] = $wkt;
}
}
Some form fields mysteriously loose
their value and need to be refilled

Wrapping it up: Placing the Geo
Data Product in the Shopping Cart
A Rule
overwrites
the line item
price with
the calculated
price

Wrapping it up: Placing the Geo
Data Product in the Shopping Cart

What it's all about...
You can build some such thing
and even more sophisticated
sites with Drupal modules
and a little coding!

Any Questions?

The End
Спасибо за внимание
Спасибі за увагу
Danke für Ihre Aufmerksamkeit
Thank you for your attention
Translated to a select
choice of languages
of planet Earth:

Drupal in aerospace - selling geodetic satellite data with Commerce - Martin Mayer

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