Diuji pada QGIS 2.18 dan QGIS 3.4
Mari kita asumsikan ada lapisan polyline yang disebut "lines"
.
Saya dapat menyarankan menggunakan "Lapisan Virtual" melalui Layer > Add Layer > Add/Edit Virtual Layer...
Ada beberapa kemungkinan kasus:
Kasus 1. Memisahkan garis menjadi segmen yang sama, pada dasarnya panjang yang sama yang ditentukan oleh pengguna.
Dengan Permintaan berikut, dimungkinkan untuk mencapai hasil. Untuk menambah / mengurangi panjang segmen, harap sesuaikan 1000 AS step_length
in -- configurations
.
-- generate series
WITH RECURSIVE generate_sections(id, sec) AS (
SELECT conf.start + 1, conf.start
FROM conf
UNION ALL
SELECT id + conf.step, sec + conf.step_length/conf.length_line
FROM generate_sections, conf
WHERE sec + conf.step_length/conf.length_line <= 1
),
-- configurations
conf AS (
SELECT
0.0 AS start,
1.0 AS step,
1000 AS step_length,
ST_Length(l.geometry) AS length_line
FROM lines AS l
)
-- query
SELECT gs.id AS id,
ROUND(ST_Length(ST_Line_Substring(l.geometry, start + sec, sec + conf.step_length/conf.length_line)),0) AS seg_length,
ST_Line_Substring(l.geometry, start + sec, sec + conf.step_length/conf.length_line) AS geom
FROM generate_sections AS gs, lines AS l, conf
GROUP BY gs.id
Output Virtual Layer akan terlihat sebagai berikut
Catatan: Jika 'delta' (misalnya yang terakhir segmen terpendek) tidak harus dimasukkan, kemudian masukkanWHERE sec_length >= step_length
dalam-- query
, lihat di bawah
-- query
SELECT gs.id AS id,
ROUND(ST_Length(ST_Line_Substring(l.geometry, start + sec, sec + conf.step_length/conf.length_line)),0) AS seg_length,
ST_Line_Substring(l.geometry, start + sec, sec + conf.step_length/conf.length_line) AS geom
FROM generate_sections AS gs, lines AS l, conf
WHERE seg_length >= step_length
GROUP BY gs.id
Kasus 2. Membagi garis menjadi sejumlah segmen tertentu
Dengan Permintaan berikut, dimungkinkan untuk mencapai hasil. Untuk menambah / mengurangi jumlah segmen, harap sesuaikan 8 AS sections
in -- configurations
.
-- generate series
WITH RECURSIVE generate_sections(id, sec) AS (
SELECT conf.start + 1, conf.start
FROM conf
UNION ALL
SELECT id + conf.step, sec + conf.step
FROM generate_sections, conf
WHERE sec + conf.step < conf.sections
),
-- configurations
conf AS (
SELECT
8 AS sections,
0.0 AS start,
1.0 AS step
)
-- query
SELECT gs.id AS id,
ST_Line_Substring(l.geometry, conf.start + sec/conf.sections, sec/conf.sections + step/conf.sections) AS geom,
ROUND(ST_Length(ST_Line_Substring(l.geometry, conf.start + sec/conf.sections, sec/conf.sections + step/conf.sections)),2) AS seg_length
FROM generate_sections AS gs, lines AS l, conf
WHERE start + step < sections
GROUP BY gs.id
Output Virtual Layer akan terlihat sebagai berikut