GIS Tools - Multi-Feature Select & Export

What Is Multi-Select and Export?

Multi-select and export is the bridge between exploration and downstream workflow. It is what lets you take a subset of features you have selected — by clicking, by drawing a lasso, by applying a filter, or by attribute query — and turn that subset into a new file. Without this step, an interactive viewer is read-only. With it, the viewer becomes a starting point for a longer pipeline that might end in a database import, a desktop GIS analysis, or a published web map.

The operation has two halves. The first is selection: how do you tell the viewer which features you care about? Common methods are click-to-add, shift-click to extend, lasso/box draw, attribute filter, spatial filter, and "select all matching" after a query. The second half is export: how do you serialize the selected features into a file format you can move elsewhere? GeoJSON is the lingua franca, but most workflows also need shapefile, KML, CSV, or GeoPackage output.

The gis.tools multi-select and export tool combines all of these methods in one interface. You can build up a selection over time, mixing and matching selection methods, and then export the resulting set as GeoJSON, shapefile, KML, CSV, GeoPackage, or copy as WKT to your clipboard. Everything happens in the browser — your selected features never leave your machine until you save the file.

This tool is the linchpin between the viewer's exploration features (filters, identify, search) and the rest of the gis.tools catalog of converters and analysis tools.

How Multi-Select Works

Selection state

Under the hood, the viewer maintains a Set of selected feature IDs for each layer. When you click a feature, its ID is added to the set. When you Shift-click, additional IDs are added. Ctrl-click toggles individual IDs. When you draw a lasso, the spatial index is queried for all features whose geometry intersects the lasso polygon, and their IDs are added in bulk.

Selection methods

The tool supports several ways to build a selection:

Click: select a single feature.
Shift-click: extend the selection.
Ctrl-click: toggle individual features.
Lasso/box draw: select all features within a drawn area.
Filter to selection: convert an attribute or spatial filter result to a selection.
Select all visible: select every feature currently rendered.
Select by ID list: paste a list of feature IDs.

Export formats

Once you have a selection, the tool serializes it to your chosen format:

GeoJSON: the web-native default, RFC 7946 compliant.
Shapefile: zipped .shp/.dbf/.prj/.shx for legacy GIS workflows.
KML: for Google Earth.
CSV: tabular with WKT or lat/lon columns.
GeoPackage: OGC SQLite container.
WKT: copy to clipboard.

Key Parameters and Options

CRS for export

Select WGS84 (EPSG:4326) for web compatibility, Web Mercator (EPSG:3857) for tile-based workflows, or any local projection via the EPSG Reprojector & Coordinate Converter.

Field subset

Choose which attribute fields to include in the export. Dropping unused fields keeps the output file small.

Geometry simplification

Apply a simplification pass on export to reduce vertex count and file size.

Practical Applications

Field crew assignment

A park manager wants to send a list of trail segments needing repair to the maintenance crew. They open the viewer, filter the trail layer for condition = 'poor', convert the filter to a selection, and export as KML. The crew loads the KML on their handheld GPS units to navigate to each segment.

Statistical sampling

A forestry researcher needs a random sample of 200 plot polygons from a larger inventory. They use the Attribute Filter Builder tool to generate the sample, multi-select the result, and export as GeoJSON for the field campaign.

Database import

A GIS analyst is migrating a project from desktop QGIS to PostGIS. They load each shapefile, select all features, export as GeoJSON, and use the Attribute Table Exporter converter to generate INSERT statements.

Targeted reporting

A city auditor needs to report on the 50 highest-cost capital projects in a downtown district. They filter the project layer by district and cost, select the top 50, and export as CSV for the report.

Publication preparation

A cartographer preparing a print map needs only the labeled features that fall within the map sheet area. They draw a lasso around the sheet boundary, select the labeled features, and export as a clean GeoJSON for the cartographic production pipeline.

Sharing with non-GIS colleagues

A biologist exports selected wildlife observation points as a CSV that her epidemiologist colleague can open in Excel without GIS software.

QA correction

After spotting bad records via the Data Profiling Report, an analyst selects the offending features, exports them, fixes the attributes externally, and reimports.

Step-by-Step Workflow

Load your data into the GeoJSON, KML, Shapefile & GIS File Viewer.
Build your selection using clicks, lasso, filters, or search.
Verify the selection count in the layer panel.
Open the export dialog and choose a format (GeoJSON, shapefile, KML, CSV, GeoPackage).
Pick the CRS (WGS84 for web, local UTM for printing).
Choose which fields to include or exclude.
Click Export — the file downloads to your local machine.
Verify the output by reopening it in another viewer or QGIS.

Worked Example

A real estate analyst working with a 47,000-parcel dataset wants to extract the parcels matching a specific buyer profile: residential, single-family, between 1500 and 3000 square feet, built after 1990, currently for sale. They start with an attribute filter using the Attribute Filter Builder:

use_type = 'SFR' AND sqft BETWEEN 1500 AND 3000 AND year_built > 1990 AND status = 'for_sale'

The filter narrows the dataset to 312 parcels. They convert the filter result to a selection, then refine by lassoing only the 187 parcels in the target school district. They export the result as GeoJSON with only address, sqft, price, and agent_phone fields. The 187-parcel file lands in their downloads folder, ready to feed into a CRM bulk import.

Common Pitfalls and Gotchas

Selection lost on layer reload. If the underlying data is replaced, the selected feature IDs may no longer exist.
Field name truncation in shapefile. DBF format limits field names to 10 characters. Long field names get truncated on export.
Encoding issues in CSV. Save as UTF-8 with BOM for Excel compatibility on Windows.
CRS confusion. Exporting WGS84 data labeled as Web Mercator (or vice versa) causes downstream errors.
Empty geometries. Selected features without geometry fail to export to formats that require it (shapefile, KML).
Browser download limits. Some browsers block files over a certain size from automatic download.
Mixed geometry types. Shapefile only supports one geometry type per file; mixed selections need separate exports.
Special characters in attribute values. Newlines and quotes in CSV cause parsing issues without proper escaping.

Tips for Best Results

Use GeoJSON as your default export format unless you specifically need shapefile compatibility.
Strip unused fields to keep output small and downstream-friendly.
Always verify the row count of the export matches your selection count.
For shapefile exports, keep field names short and ASCII.
Use the GeoJSON Validator & Fixer on exports before downstream use.
Save the original selection criteria (filter expression) alongside the export for reproducibility.
For very large selections, consider exporting in chunks.
Keep field names lowercase and snake_case for cross-tool compatibility.

Comparison with Desktop GIS

QGIS implements this as Save Selected Features As, accessible from the right-click layer menu. ArcGIS uses Export Data on a selection. Both desktop tools support the same set of formats and CRS choices but require a longer click path. The gis.tools approach optimizes for the common case: pick a format, click export, get a file.

The browser-based version cannot export to enterprise database formats (Oracle Spatial, SQL Server Spatial), but for the formats it does support, the workflow is faster and requires no project setup.

Performance Considerations

Export speed scales linearly with selection size. A 10,000-feature GeoJSON exports in under a second. Shapefile export is slower because of the binary encoding and the need to zip the four component files. CSV is the fastest. For selections over a million features, expect multi-second exports and consider chunking.

Data Privacy and Browser-Based Processing

The export operation runs entirely in the browser. The selected features are serialized in memory and saved directly to your local downloads folder via a Blob URL — they never travel to a server. This makes the tool safe for confidential business data, personal information, and any other content that cannot be uploaded to third-party services.

Related GIS Concepts

Selection set. The collection of currently selected features in a viewer.

Save As / Export. Persisting a subset of in-memory data to a file format.

Format conversion. Translating between data representations (GeoJSON ↔ shapefile, etc.).

Attribute schema. The list of fields and their types in a vector dataset.

Frequently Asked Questions

Can I export only some fields?

Yes. The export dialog has a field picker that lets you include or exclude specific fields.

What format should I use?

GeoJSON for web workflows, shapefile for legacy GIS, KML for Google Earth, CSV for spreadsheets.

How do I select features?

Click, shift-click, lasso, or convert a filter result to a selection.

Why is my shapefile export missing fields?

DBF truncates field names to 10 characters. Rename long fields before export.

Can I export to PostGIS directly?

Not directly, but you can export to GeoJSON and use the Attribute Table Exporter converter.

Tips